Jump to letter: A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A

AADC

See aromatic amino acid decarboxylase. [5, 6]

AAS

See anabolic–androgenic steroids. [16]

absolute refractory period

Short period of time after an action potential when Na⁺ channels close and are refractory until repolarization to resting potential occurs. [2]

absorption

Movement of a drug from the site of administration to the circulatory system. [1]

abstinence syndrome

Condition characterized by unpleasant symptoms when an individual tries to cease drug use. [9, 11]

acamprosate (Campral)

Partial antagonist at NMDA receptors used for the treatment of alcoholism. [10]

acetyl coenzyme A (acetyl CoA)

Precursor necessary for ACh synthesis. [7]

acetylcholine (Ach)

Neurotransmitter involved with the central and peripheral nervous system and synthesized by the cholinergic neurons. It is the target of many of the deadliest neurotoxins. [7]

acetylcholinesterase (AChE)

Enzyme that controls levels of ACh by breaking it down into choline and acetic acid. [7]

Ach

See acetylcholine. [7]

AChE

See acetylcholinesterase. [7]

ACTH

See adrenocorticotropic hormone. [3]

action potential

Major depolarization generated in the axon hillock that is transmitted down the axon. [2]

active zones

Areas along the axon terminal, near the postsynaptic cell, that are specialized for neurotransmitter release. [3]

acute tolerance

Rapid tolerance formed during a single administration of a drug, as is the case with alcohol. [1, 10]

additive effects

Drug interactions characterized by the collective sum of the two individual drug effects. [1]

adenosine

Blockade of receptors for this substance is responsible for caffeine’s stimulant effects. [13]

adoption studies

Studies used to understand how heredity contributes to a disorder by comparing the incidence of the disorder in the biological and adoptive parents of people adopted at an early age who have the disorder. A higher incidence of the disorder among biological parents than adoptive parents suggests a hereditary influence. [18]

adrenal cortex

Outer portion of the adrenal gland that secretes glucocorticoids. [3]

adrenal glands

Endocrine glands that are located above the kidney and secrete EPI, NE, and glucocorticoids. An adrenal gland is composed of the adrenal medulla and the adrenal cortex. [3]

adrenal medulla

Inner portion of the adrenal gland that secretes the catecholamines EPI and NE. [3]

adrenergic

Adjectival form of adrenaline, also called epinephrine (EPI). May be used broadly to include both NE- and EPI-related features. [5]

adrenoceptors

Receptors to which NE and EPI bind; part of the metabotropic receptor family. Also known as an adrenergic receptors. [5]

adrenocorticotropic hormone (ACTH)

Hormone secreted by the anterior pituitary that stimulates glucocorticoid synthesis and release from the adrenal cortex.

affinity

Ability of a molecule to bind to a receptor, which then determines potency. [1]

afterglow

Desired subjective state that may follow the peak experience produced during a hallucinogenic drug-assisted therapeutic session. [15]

agoraphobia

Fear of public places. [17]

akathisia

Constant urge to move certain body parts. [20]

akinesia

Difficulty in initiating movement. [20]

albuterol (Ventolin)

Drug that selectively stimulates the β-adrenoceptor. It is used in asthma treatments. [5]

alcohol

Ethyl alcohol is an organic compound that is a product of fermentation and belongs to the class of sedative–hypnotics. [17]

alcohol dehydrogenase

Enzyme in the liver and stomach that oxidizes alcohol into acetaldehyde. [10]

alcohol or barbiturate withdrawal

Symptoms associated with the termination of alcohol, barbiturate, or benzodiazepine use. The three drugs are cross dependent; administration of one alleviates withdrawal symptoms of the other. [17]

alcohol poisoning

Toxic effects associated with the ingestion of excess alcohol, characterized by unconsciousness, vomiting, irregular breathing, and cold, clammy skin. [10]

alcohol use disorder

A form of substance abuse characterized by compulsive alcohol seeking and use despite damaging social and health effects. Formerly called alcoholism. [10]

alcohol-induced cirrhosis

Condition seen in chronic alcohol abusers caused by scar tissue formation that promotes cell death as scar tissue cuts off blood supplies. [10]

alcohol-induced hepatitis

Condition seen in chronic alcohol abusers caused by death of liver cells and characterized by inflammation of the liver, fever, jaundice, and pain. [10]

aldehyde dehydrogenase (ALDH)

Enzyme in the liver that metabolizes the acetaldehyde intermediate formed by alcohol oxidation into acetic acid. [10]

ALDH

See aldehyde dehydrogenase. [10]

allodynia

Condition characterized by painful responses to stimuli that do not normally cause pain. [6]

allostasis

Adaptive biological process in which an organism’s response to repeated threats or challenges results in long-lasting physiological or behavioral changes. This concept is distinguished from homeostasis, which refers to the tendency of an organism to maintain physiological or behavioral stability in the face of threats or challenges (i.e., to remain unchanged). [9]

allosteric modulators

Compounds that bind to a receptor site distinct from the main agonist binding site, may or may not have an effect on the receptor when administered alone, and either enhance (in the case of a positive allosteric modulator) or reduce (in the case of a negative allosteric modulator) the effectiveness of an agonist on the receptor. They have potential therapeutic use because of their ability to tune receptor activity more subtly than either a receptor agonist or an antagonist. [3, 7]

allosteric sites

Binding sites on a receptor protein that modulate the receptor’s response, either positively or negatively, to a receptor agonist. [3]

allylglycine

Drug that blocks GABA synthesis, inducing convulsions. [8]

alosetron (Lotronex)

Drug that inhibits 5-HT₃ receptors. It is used to treat the diarrhea-predominant form of irritable bowel syndrome. [6]

α-methyl-para-tyrosine (AMPT)

Drug that inhibits TH activity, thereby reducing catecholamine synthesis. [5]

α-PVP

Cathinone derivative (α-pyrrolidinovalerophenone) that is an abused stimulant drug. It is a member of a group of compounds sometimes called “bath salts,” “plant food,” “pond water cleaner,” and “legal highs.” [12]

5α-reductase

Enzyme that converts testosterone to 5α-dihydrotestosterone. [16]

α-synuclein

A protein that is found primarily in neurons and accumulates to form Lewy bodies in people affected with Parkinson’s disease and some forms of dementia. [20]

ALS

See amyotrophic lateral sclerosis. [8]

altered states of consciousness (ASC) rating scale

Psychometric scale developed to quantify the subjective effects of hallucinogenic agents. [15]

Alzheimer’s disease

Neurodegenerative disorder, almost always occurring in the elderly, which is characterized behaviorally by progressive loss of cognitive function and histologically by the presence of extracellular plaques containing beta-amyloid protein and intracellular neurofibrillary tangles containing hyperphosphorylated tau protein. It is the most common cause of dementia. [7, 20]

amino acids

Essential building blocks of proteins, some of which also act as neurotransmitters. [3]

amotivational syndrome

Symptoms of cannabis use that relate to poor educational achievement and motivation. [14]

AMPA receptor

An ionotropic glutamate receptor selective for the synthetic amino acid agonist AMPA. [8]

ampakines

Class of cognitive enhancing drugs that work by inhibiting the desensitization of glutamate AMPA receptors. [8]

amphetamine-induced stereotypy

Model for schizophrenia induced by giving animals high doses of amphetamine to produce repetitive, stereotyped behavior. [19]

amphetamine

Psychostimulant that acts by increasing catecholamine release in nerve cells. [5, 12]

AMPT

See α-methyl-para-tyrosine. [5]

amygdala

Part of the limbic system that helps to modulate emotional behavior and coordinates the various components of emotion. [2]

amyloid precursor protein (APP)

Transmembrane protein. Cleavage by secretases forms Aβ. [20]

amyotrophic lateral sclerosis (ALS)

Neurological disorder characterized by degeneration of the motor neurons of the spinal cord and cortex. Also known as Lou Gehrig’s disease. [8]

anabolic–androgenic steroids (AAS)

Group of performance enhancers characterized by their ability to increase muscle mass and produce masculine qualities. The name may be shortened to anabolic steroids. [16]

analeptics

Drugs that act as circulatory, respiratory, or general CNS stimulants. [15]

anandamide

Common chemical name of the arachidonic acid derivative that functions as an endogenous ligand for cannabinoid receptors in the brain. [14]

androgen receptor

Target site of testosterone and other androgens, located within the cytoplasm of the cell and present in many tissues. [16]

androgens

Male sex hormones secreted by the testes. [3]

anesthetics

General anesthetics are substances that depress the CNS, decreasing all sensations in the body and causing unconsciousness. Local anesthetics do not cause unconsciousness, but prevent pain signals by blocking Na⁺ channels. Some anesthetics such as nitrous oxide (also known as laughing gas), chloroform, and ether comprise a class of abused inhalant substances. [11, 16]

anhedonia

Difficulty or lack of the ability to experience pleasure. Such a state is characteristic of many depressed patients and may also occur during drug withdrawal in an addicted person. [9]

anorectic

Having the effect of reducing appetite. [6]

anosmia

Inability to perceive odors. [20]

Antabuse

See disulfiram. [10]

anterior pituitary

Portion of the pituitary gland that secretes the hormones TSH, ACTH, FSH, LH, GH, and PRL. [3]

anterior

Located near the front or head end of an animal. [2]

anteropulsion

Feeling of being pushed forward. [20]

antibody

Protein produced by the immune system for the purpose of recognizing, attacking, and destroying a specific foreign substance (i.e., an antigen). [4]

anticipatory anxiety

Feeling of extreme worry over the possibility that a certain unpleasant event will occur in a particular, often public, situation. [17]

anticonvulsants

Drugs, such as benzodiazepines, that prevent or control seizures. They are used to treat epilepsy. [17]

antireward system

System within the brain that is recruited during the withdrawal/negative affect stage of the addiction spiral and plays an important role in the transition from controlled to compulsive drug use. Key components include the central amygdala and the neurotransmitters NE and CRF. [9]

antitussives

Drugs that suppress the coughing reflex. [15]

anxiolytics

Drugs that alleviate feelings of anxiety in humans and that reduce anxiety-related behaviors in animals. [17]

apnea

Cessation of breathing. [6]

apolipoprotein E (ApoE)

Protein that helps break down amyloid. Individuals carrying the E4 allele of the gene encoding this protein develop AD. [20]

apomorphine

Drug that is a D₁ and D₂ receptor agonist and causes behavioral activation. It may also be used to treat erectile dysfunction by acting through DA receptors in the brain to increase penile blood flow. [5]

apoptosis

Cell death resulting from a programmed series of biochemical events designed to eliminate unnecessary cells. It may also be called programmed cell death. [8]

APP

See amyloid precursor protein. [20]

arachidonoyl ethanolamide (AEA)

Formal chemical name of anandamide. [14]

2-arachidonoylglycerol (2-AG)

An arachidonic acid derivative that functions as an endogenous ligand for brain cannabinoid receptors. [14]

arachnoid

Membrane consisting of a weblike sublayer that covers the brain and spinal cord and contains CSF. One of the three meninges. [2]

area postrema

Area in the medulla of the brain stem that is not isolated from chemicals in the blood. It is responsible for inducing a vomiting response when a toxic substance is present in the blood. [2]

arecoline

Chemical from the seeds of the betel nut palm Areca catechu that stimulates muscarinic receptors. [7]

aromatase

Enzyme that converts testosterone to estradiol. [16]

aromatic amino acid decarboxylase (AADC)

Enzyme that catalyzes the removal of a carboxyl group from certain amino acids. It is responsible for the conversion of DOPA to DA in catecholaminergic neurons and the conversion of 5-HTP to 5-HT in serotonergic neurons. [5, 6, 20]

Artane

See trihexyphenidyl. [7]

ASC

See Altered States of Consciousness rating scale. [15]

aspartate

Ionized form of aspartic acid. It is an excitatory amino acid neurotransmitter of the CNS. [8]

association analysis

Determination of whether a particular genetic polymorphism is associated with a particular disease or trait. [10]

astrocytes

Star-shaped glial cells that have numerous extensions and that modulate the chemical environment around neurons, metabolically assist neurons, and provide phagocytosis for cellular debris. [1, 2]

astroglia

The collective terms for astrocytes. [1]

atomoxetine (Strattera)

Selective norepinephrine uptake inhibitor used in the treatment of ADHD. [5]

atropine

Drug found in nightshade, Atropa belladonna, and henbane, Hyoscyamus niger, that blocks muscarinic receptors. [7]

attentional set-shifting task

Rodent version of the WCST in which the animals must choose the bowl with the food reward based on either odor or surface texture. [19]

autoimmune disorder

Condition in which the immune system attacks part of one’s own body. [7]

autoradiography

Process used to detect the amount and location of bound radioligand by using a specialized film to create an image of where the radioligand is located within a tissue slice. [4]

autoreceptors

Neuronal receptors in a cell that are specific for the same neurotransmitter released by that cell. They typically inhibit further neurotransmitter release. [3]

autosomal dominant Alzheimer’s disease (ADAD)

Familial version of AD caused by mutations in the genes for presenelin-1, presenilin-2, and amyloid precursor protein. [20]

axoaxonic synapses

Junctions used for communication between the axon terminals of two neurons, permitting the presynaptic cell to control neurotransmitter release from the postsynaptic cell at the terminals. [3]

axodendritic synapses

Junction used for communication between the axon terminal of a presynaptic neuron and a dendrite of a postsynaptic neuron. [3]

axon

Long tubular extention from the soma of the nerve cell that conducts electrical signals away from the cell body and toward the axon terminals. [2]

axon collaterals

Branches formed when an axon splits, giving the neuron the ability to signal more cells. [2]

axon hillock

The segment of axon adjacent to the soma where the action potential is first generated. [2]

axoplasmic transport

Method of transporting proteins along the microtubules of the cytoskeleton to designations throughout a neuron. Anterograde transport moves newly synthesized proteins from the soma. Retrograde transport moves waste back to the soma from the terminals. [2]

axosomatic synapses

Junctions used for communication between a nerve terminal and a nerve cell body. [3]

ayahuasca

Hallucinogenic mixture originating in the Amazon rain forest. It typically contains stalks from the Banisteriopsis caapi vine and leaves from Psychotria viridis and/or Diplopterys cabrerana. Together, these plants provide the hallucinogenic tryptamine DMT along with β-carbolines that inhibit MAO and permit the DMT to reach the brain when the ayahuasca is consumed orally. [15]

Azilect

See rasagiline. [5]

B

BAC

See blood alcohol concentration. [10]

baclofen (Lioresal)

Drug that is a selective agonist for the GABA_B receptors. It is used as a muscle relaxant and an antispastic agent. [8]

barbiturates

Drugs that act as a CNS depressant, in part by enhancing GABA_A receptor activity. [8]

basal forebrain cholinergic system (BFCS)

Collection of cholinergic nerve cells that innervates the cerebral cortex and limbic system structures. Damage to this system contributes to the symptoms of Alzheimer’s disease. [7]

basal ganglia

Nuclei of the telencephalon that includes the caudate, putamen, and globus pallidus. The structures help regulate motor control. [2, 20]

BDNF

See brain-derived neurotrophic factor. [18]

BDZs

See benzodiazapine. [8]

beam walking

Device resembling a human gymnastics balance beam used to evaluate rodent fine motor coordination and balance. [4]

behavioral addictions

Uncontrolled behaviors not involving substance use but that have characteristics similar to those seen in substance-related disorders. [9]

behavioral desensitization

Technique used to treat phobias by introducing the fear-inducing stimulus in increments, allowing the patient to maintain a relaxed feeling in its presence. [17]

behavioral despair

Technique used to measure depression in animals by placing them in a cylinder of water from which they cannot escape and recording the time it takes for them to abandon attempts to escape. [4]

behavioral supersensitivity

An increased response to a drug treatment as a direct result of previous drug history or drug intake. [5]

behavioral tolerance

The reduced effectiveness of a drug administered chronically that involves learning: either instumental or classical conditioning. [1, 10]

benzodiazepines (BDZs)

Drugs that act as a CNS depressants, in part by enhancing GABA_A receptor activity. [8]

benzoylecgonine

Major metabolite of cocaine. [12]

benztropine mesylate (Cogentin)

Anticholinergic drug used to treat early symptoms of Parkinson’s disease. [7]

beta-amyloid protein (β-amyloid or A-beta [Aβ])

Protein fragment derived from enzymatic cleavage of amyloid precursor protein. Primary component of the plaques characteristic of Alzheimer’s disease. Also called A-beta and Aβ. [20]

β-carboline

An inverse agonist at the BDZ modulatory site on GABA_A receptors that makes GABA less effective in producing hyperpolarization. It is anxiogenic and is a useful tool in studying the neurobiology of anxiety. [17]

BFCS

See basal forebrain cholinergic system. [7]

bicuculline

Drug that blocks the binding of GABA to the GABA_A receptor and acts as a convulsant. [8]

binge drinking

Consumption of five or more alcoholic drinks within a 2-hour period. [10]

bioactivation

A metabolic process that converts an inactive drug into an active one. [1]

bioavailability

Concentration of drug present in the blood that is free to bind to specific target sites. [1]

biogenic amine

A transmitter that is made by a living organism and contains at least one amine group. [5]

biopsychosocial model

Model of addiction that attempts to give a full account of addiction by incorporating biological, psychological, and sociological factors. [9]

biotransformation

Inactivation of a drug through a chemical change, usually by metabolic processes catalyzed by enzymes in the liver. [1]

bipolar disorder

Type of affective disorder characterized by extreme mood swings between depression and mania. [18]

blackout

Amnesia directly associated with heavy alcohol consumption. [10]

blood alcohol concentration (BAC)

The amount of alcohol in a given unit of blood, usually given as a percent representing milligrams of alcohol per 100 milliliters of blood. [10]

bradykinesia

General slowing of movement that is characteristic of Parkinson’s disease. Examples include slowed movement of facial muscles leading to “stone-faced” expression and reduced hand movement resulting in micrographia (smaller handwriting). [20]

bradyphrenia

Slowed response to questioning. [20]

brain-derived neurotrophic factor (BDNF)

Protein of the CNS that stimulates cell proliferation, aids in cell survival and synaptic restructuring. It is also implicated in the neurotrophic hypothesis of depression. [8, 18]

brainstem

Portion of the brain, consisting of the medulla, pons, and midbrain. [2]

breaking point

The point at which an animal will no longer expend the effort required to receive the reward (e.g., in a drug self-administration paradigm). [4, 9]

breakpoint

See breaking point. [9]

bridging

Pattern of anabolic–androgenic steroid use in which a low dose is used to bridge between each high dose of the steroid (also called “blast and cruise”). [16]

broad-spectrum antipsychotics

Class of drugs used to treat schizophrenia by blocking a wide range of receptors in addition to the D₂ receptor. [19]

bufotenine

Tryptamine hallucinogen present in the toxic secretions of an American desert toad, Bufo alvarius. [15]

bulk endocytosis

Mechanism for retrieval of large amounts of synaptic vesicle membrane after very strong or prolonged neuronal firing. [3]

Buprenex

See buprenorphine. [11]

buprenorphine(Buprenex)

An opioid agonist–antagonist used in opioid treatment programs that may be substituted for methadone and yields similar treatment results. [11]

bupropion (Zyban)

Drug that inhibits DA and NE uptake and is also a weak nAChR antagonist. It is used in the treatment of tobacco dependence. [13]

burst mode

Mode of neuronal cell firing characterized by the production of bursts of action potentials. [5]

buspirone (BuSpar)

Drug that is a partial agonist at 5-HT_1A receptors. Symptoms include increased appetite, reduced anxiety, reduced alcohol cravings, and a lower body temperature. It is prescribed as an antianxiety medication that lacks sedation, mental clouding, potential for abuse, or physiological dependence. [6, 17]

C

c-fos

Transcription factor that rises rapidly within cells during increased neural activity. [4]

caffeine

Stimulant drug found naturally in coffee and tea. It is also consumed in tablet form and in various beverages such as such drinks and energy drinks. [13]

caffeine dependence syndrome

Disorder produced by chronic high-dose caffeine use and characterized by caffeine craving, difficulty controlling caffeine consumption, caffeine tolerance, and withdrawal symptoms that occur following abstinence. It is a recognized disorder within ICD-10 but not within DSM-5. [13]

caffeine intoxication

Disorder produced by recent high-dose caffeine use and characterized by symptoms of restlessness, nervousness, insomnia, and physiological disturbances including tachycardia (increased heart rate), muscle twitching, and gastrointestinal upset. [13]

caffeine use disorder

DSM-5 category with features similar to those of caffeine dependence syndrome. It is not a recognized disorder but has been designated for additional research. [13]

calcium/calmodulin kinase II (CaMKII)

Enzyme stimulated by calcium and calmodulin that phosphorylates specific proteins in a signaling pathway. [3]

cAMP

See cyclic adenosine monophosphate. [3]

Campral

See acamprosate. [10]

candidate gene analysis

Analysis of a gene that is suspected of involvement in the development, progression, or manifestation of a disease. [9]

candidate genes

Genes that are suspected of involvement in the development, progression, or manifestation of a disease. [19]

cannabidiol (CBD)

Phytocannabinoid that lacks the intoxicating and dependence-producing effects of THC. [14]

cannabinoid receptor

Receptor for cannabinoids, including THC and anandamide. In the CNS, they are concentrated in the basal ganglia, cerebellum, hippocampus, and cerebral cortex. [14]

Carbamazepine (Tegretol)

An anticonvulsant drug used to treat bipolar disorder. [18]

carbidopa

A decarboxylase inhibitor that cannot cross the blood–brain barrier. Increases the availability of l-DOPA to the brain. [6, 20]

case–control method

Technique used to identify genes associated with a disorder by comparing the genes of unrelated affected and unaffected people to determine if those who are affected are more likely to possess a particular allele. [10]

catalepsy

State characterized by a lack of spontaneous movement. It is usually associated with D₂ receptor blockers (a DA receptor subtype), but can also be induced with a D₁ blocker. [4, 5]

cataplexy

Loss of muscle control in patients with narcolepsy that is usually triggered by a strong emotion such as laughing or becoming angry or frustrated. [3]

Catapres

See clonidine. [5]

catechol-O-methyltransferase (COMT)

One of the enzymes responsible for metabolic breakdown of catecholamines. [5, 20]

catecholamines

Group of neurotransmitters and hormones characterized by two chemical similarities: a core structure of catechol and a nitrogen-containing amine. They belong to a wider group of transmitters called monoamines or biogenic amines. [5]

cathinone

Psychostimulant that is the primary active ingredient in khat. [12]

caudal

The tail end of the nervous system is caudal or posterior. [2]

CB1

Cannabinoid receptor of the metabotropic receptor family located in the CNS. [14]

CB2

Cannabinoid receptor located primarily in the immune system. [14]

CBD

See cannabidiol. [14]

central canal

Channel within the center of the spinal cord filled with CSF. [2]

cerebellar peduncles

Large bundles of axons that connect the cerebellum to the pons. [2]

cerebellum

Large structure of the metencephalon that is located on the dorsal surface of the brain and that is connected to the pons by the cerebellar peduncles. It is an important sensorimotor control center of the brain. [2]

cerebral ventricles

Cavities within the brain filled with CSF. [2]

cerebrospinal fluid (CSF)

Fluid that surrounds the brain and spinal cord, providing cushioning that protects against trauma. It also fills the cerebral ventricles and the central canal of the spinal cord. [1]

cGMP

See cyclic guanosine monophosphate. [3]

Chantix

See varenicline. [13]

ChAT

See choline acetyltransferase. [7]

chemogenetics

The activation or suppression of a genetically engineered receptor with a designer ligand in order to study behavioral effects of longer duration compared to optogenetic manipulation. Sometimes referred to ad DREADD. [4]

chlorogenic acids

Class of chemicals present within brewed coffee that are hypothesized to confer a protective effect against the development of type 2 diabetes among people who drink at least three to four cups of coffee per day. [13]

choline acetyltransferase (ChAT)

Enzyme that catalyzes the synthesis of ACh from acetyl CoA and choline. [7]

choline transporter

Protein in the membrane of the cholinergic nerve terminal involved with the uptake of choline from the synaptic cleft. [7]

choline

Precursor necessary for ACh synthesis. [7]

cholinergic

Adjectival form of ACh. [7]

cholinesterase inhibitors

Drugs that improve cognitive symptoms by increasing the presence of acetylcholine in the synapse by lessening breakdown of ACh. One of two categories of treatment for AD. [20]

chromaffin cells

The cells of the adrenal medulla. [3]

chromatin remodeling

One type of environmentally-induced epigenetic modification that increases or decreases gene transcription. [2]

chromosomes

Double helical strands of DNA that carry genes. [2]

chronic mild unpredictable stress

Rodent model of depression created by exposing animals to a series of stressful events in an unpredictable fashion. [4]

chronic obstructive pulmonary disease (COPD)

Disorder of the respiratory system characterized by shortness of breath, wheezing, chronic coughing, and chest tightness. Two main conditions comprise COPD, namely emphysema and bronchitis. [13]

chronic social defeat stress

Rodent model of depression created by the intense stress of being repeatedly placed as an intruder in a cage with a resident animal. [4]

classical conditioning

Repeated pairing of a neutral stimulus with an unconditioned stimulus. Eventually the neutral stimulus becomes a conditioned stimulus and elicits a (conditioned) response that is similar to the original unconditioned response. This type of learning has a role in drug use and tolerance. [1]

clathrin

Protein that participates in synaptic vesicle recycling, either in the endocytotic step of retrieving vesicle membrane from the axon terminal membrane or in the budding of new vesicles from endosomes in the axon terminal. [3]

clathrin-mediated endocytosis

Process of synaptic vesicle membrane recovery that relies on the protein clathrin. [3]

clonidine (Catapres)

An α₂-adrenergic agonist that stimulates autoreceptors and inhibits noradrenergic cell firing. It is used to reduce symptoms of opioid withdrawal. [5]

clonidine

An α2-adrenergic agonist that stimulates autoreceptors and inhibits noradrenergic cell firing. It is used to reduce symptoms of opioid withdrawal. [11]

cloning

Method used to produce large numbers of genetically identical cells. [4]

closed

State of a receptor channel in which the channel pore is closed, thereby preventing ion flow across the cell membrane. [7]

clozapine (Clozaril)

Drug that inhibits 5-HT_2A and D₂ dopamine receptors. It is used to treat schizophrenia. [6]

club drug

Street name for GHB, as well as MDMA and ketamine, coined as a result of their popularity at nightclubs. [16]

CNS depressants

Large category of drugs that inhibit nerve cell firing within the central nervous system. They include sedative–hypnotics and are used to induce sleep and to treat symptoms of anxiety. [17]

co-agonists

Substances needed simultaneously to activate a specific receptor. [8]

cocaethylene

Metabolite formed from the interaction of cocaine and alcohol. It produces biological effects similar to those of cocaine. [12]

cocaine

Stimulant drug that blocks reuptake of DA, NE, and 5-HT by neurons, thereby increasing their concentration in the synaptic cleft. [5, 12]

cocaine binges

Periods of cocaine use lasting hours or days with little or no sleep. [12]

coding region

Portion of the gene that codes for the amino acid sequence of a protein. [2]

Cogentin

See benztropine mesylate. [7]

cognitive behavioral therapy (CBT)

Type of psychotherapy that can be used to treat drug addiction by restructuring the drug user’s cognitive (thought) processes and training the user either to avoid high-risk situations that might cause relapse or to employ appropriate coping mechanisms to manage such situations when they occur. [12]

cognitive symptoms

A category of symptoms of schizophrenia that includes impaired working memory, poor executive function, and attention deficits. [19]

common disease–common variant hypothesis

Hypothesis that genetically based susceptibility to a particular neuropsychiatric disorder stems from a pool of risk-conferring gene alleles that are possessed in common throughout the population. Each of these “risk alleles” confers a small increase in susceptibility to developing the disorder. [9]

common disease–rare variant hypothesis

Hypothesis that genetic risk for a neuropsychiatric disorder stems from rare mutations or other genetic anomalies such as copy number variations (variable numbers of repeated stretches of DNA). It is alternative to the common disease–common variant hypothesis. [9]

comorbidity

Diagnosis of simultaneous but distinct disease processes in an individual, such as the propensity for drug abusers to be diagnosed with other psychiatric problems. [9]

competitive antagonist

Drug that binds to a receptor but has little or no efficacy. When it competes with an agonist for receptor sites, it reduces the effect of the agonist. [1]

compulsions

Repetitive tasks that an individual feels obligated to complete in an effort to quell the anxiety caused by obsessive thoughts. [17]

computerized tomography (CT)

X-ray based technique that provides computer-generated “slices” through the brain or body part that can be computer reconstructed into 3-dimensional images. [4]

COMT

See catechol-O-methyltransferase. [5]

Comtan

See entacapone. [5]

concentration gradient

Difference in the amount or concentration of a substance on each side of a biological barrier, such as the cell membrane. [1]

conditioned emotional response

Learned response to a neutral stimulus presented just prior to a negative stimulus (e.g., an electric shock) in an effort to create a fear association to the neutral stimulus. [4]

conditioned place preference

Method used to determine the rewarding effects of a drug by allowing an animal to associate the drug with a specific environment and measuring its subsequent preference for that environment. [4]

conflict procedure

Method that creates a dilemma for an animal by giving it the choice of selecting a reward that is accompanied by a negative stimulus. Conflict procedures screen drugs for antianxiety effects. [4]

construct validity

Term that represents the extent to which the animal measurement tool actually measures the human characteristic of interest. [4]

contingency management program

Type of addiction treatment program in which the client’s drug taking is monitored by regular urine testing and abstinence is reinforced with vouchers redeemable locally for consumer products or services. [12]

contingency management

Type of addiction treatment program in which the client’s drug taking is monitored by regular urine testing and abstinence is reinforced with vouchers redeemable locally for consumer products or services. [9]

convergence

Process by which neurons receive and integrate the numerous signals from other cells. [2]

COPD

See chronic obstructive pulmonary disease. [13]

core

Following an ischemic stroke, this is the inner region of damage within which the dying neurons cannot be rescued. [8]

coronal

Sections cut parallel to the face. [2]

corpus callosum

Large pathway connecting corresponding areas of the two brain hemispheres, allowing communication between each half of the brain. [2]

correlational relationship

Connection between two events that appear related, but cannot be assumed to be cause and effect. [4]

corticosterone

Glucocorticoid secreted by the adrenal cortex of rats and mice. [3]

corticotropin-releasing hormone (CRH)

Hormone synthesized by neurons of the hypothalamus that stimulates ACTH release. Also known as corticotrophin-releasing factor (CRF). [3]

cortisol

Specific glucocorticoid secreted by the adrenal cortex of primates. [3]

cotinine

Principal product of nicotine metabolism by the liver. [13]

COX-2

See cyclooxygenase-2. [14]

crack

Form of cocaine made by adding baking soda to a solution of cocaine HCl, heating the mixture, and drying the solid. [12]

craving

Strong urge addicts feel, compelling them to take a drug. [9]

CRF₁ antagonists

A drug that binds to CRF₁ receptors and produces little or no conformational change. In the presence of a CRF agonist, the agonist effect is reduced. [10]

CRH

See corticotropin-releasing hormone. [3]

CRISPR

Acronym for clustered regularly interspaced short palindromic repeats. A faster and less expensive way to create genetically engineered mice. The technique uses a “guide RNA” to locate a specific gene sequence that is then cut out or replaced. [4]

cross dependence

Withdrawal signs occurring in a dependent individual can be terminated by administering drugs in the same class. [10, 11]

cross-tolerance

Tolerance to a specific drug can reduce the effectiveness of another drug in the same class. [1, 10, 11]

CSF

See cerebrospinal fluid. [1]

CT

See computerized tomography. [4]

cyclic adenosine monophosphate (cAMP)

Second messenger that activates PKA and is controlled by DA, NE, 5-HT, and endorphins. [3]

cyclic guanosine monophosphate (cGMP)

Second messenger that activates PKG and is controlled in part by NO. [3]

cycling

Pattern of steroid use characterized by 6 to 12 weeks of drug use, followed by a period of abstinence before repeating the drug use pattern. [16]

cyclooxygenase-2 (COX-2)

Enzyme that can metabolize endocannabinoids and that plays an important role in the process of inflammation. [14]

CYP450

See cytochrome P450. [1]

cytochrome P450 (CYP450)

Class of liver enzymes, in the microsomal enzyme group, responsible for both phase 1 and phase 2 biotransformation of psychoactive drugs. [1]

cytochrome P450

Class of liver enzymes, in the microsomal enzyme group, responsible for both phase 1 and phase 2 biotransformation of psychoactive drugs. [10]

cytochrome P450 2A6 (CYP2A6)

Specific type of cytochrome P450 that metabolizes nicotine into cotinine. [13]

cytoplasm

Salty gelatinous fluid of the cell, outside of the nucleus and bounded by the cell membrane. [2]

cytoskeleton

Structural matrix of a cell that is composed of tubular materials such as microtubules and neurofilaments. [2]

D

d-serine

Amino acid that is a co-agonist with glutamate for the NMDA receptor. [8]

d-tubocurarine

Poison that targets muscle nicotinic receptors, blocking cholinergic transmission. [7]

DA imbalance hypothesis

Theory that excessive DA function of mesolimbic neurons produces positive symptoms and insufficient DA function of mesocortical neurons produces negative and cognitive symptoms of schizophrenia. [19]

DA transporter

Protein in the membrane of dopaminergic neurons that is responsible for DA uptake from the synaptic cleft. [5]

DA

See dopamine. [5]

dabbing

Form of high-potency cannabis consumption. It typically involves extraction of cannabis with butane, evaporation of the solvent, and then smoking the resulting waxy residue. [14]

DAG

See diacylglycerol. [3]

DBH

See dopamine β-hydroxylase. [5]

delayed match-to-sample

Behavioral task used to test short-term memory. [8]

delirium tremens (DTs)

Severe effects of alcohol withdrawal characterized by irritability, headaches, agitation, hallucinations, and confusion. [10]

δ-receptors

A type of opioid receptor primarily in the forebrain that may help regulate olfaction, motor integration, reinforcement, and cognitive function. [11]

Δ⁹-tetrahydrocannabinol (THC)

Psychoactive chemical found in cannabis plants; a cannabinoid. [14]

ΔFosB

Member of the Fos family of transcription factors. This protein accumulates in some brain areas after repeated exposure to various drugs of abuse and is hypothesized to contribute to the development of an addicted state. [9]

dendrites

Projections from the soma that receive signals and information from other cells. [2]

dendritic spines

Projections from dendrites that increase the receiving surface area. [2]

2-deoxyglucose autoradiography

A research tool that visually identifies neurons that are active by measuring glucose uptake. [4]

Depakote

See valproate. [18]

depolarization

Change in membrane potential making the inside of the cell more positive, increasing the likelihood that the cell will have an action potential. [2]

depolarization block

Process in which the resting potential across the cell membrane is lost. The neuron cannot be excited until the membrane is repolarized. [7]

depot binding

Type of drug interaction involving binding to an inactive site, such as to proteins in the plasma, to bone, or to fat. [1]

deprivation reversal model

Theory that smoking is maintained by mood enhancement and increased concentration that occur when nicotine withdrawal symptoms are alleviated. [13]

descending modulatory pathways

Bundles of nerve fibers originating at higher brain regions that influence lower brain or spinal cord function. One arises from the PAG in the midbrain and influences pain signals carried by the spinal cord neurons. [11]

desensitization

Process by which an ionotropic channel receptor remains closed despite the presence of an agonist bound to the receptor. The receptor cannot respond again until it leaves the desensitized state. [3]

desensitized

Altered receptor state characterized by a lack of response to an agonist. [7]

detoxification

Procedure used to treat addicted individuals in which the drug is stopped and withdrawal symptoms are treated until the abstinence syndrome has ended. [10]

detoxified

A drug user undergoing detoxification is considered to be detoxified when signs of the abstinence syndrome end. [11]

developmental origins of health and disease

Hypothesis that postulates that characteristics of the intrauterine environment, such as nutrient availability and the presence of drugs, environmental toxins, or infectious agents, “program” the fetus in a way that determines the vulnerability for developing chronic diseases in adulthood. [13]

dexamethasone

A synthetic corticosteroid used to test the function of the negative feedback mechanism regulating the HPA axis. [18]

dexmedetomidine (Precedex)

Drug that stimulates α2-receptors, characterized by its sedative, anxiolytic, and analgesic effects. It is used to treat surgical patients in intensive care. [5]

dextromethorphan

Opioid-like drug that is the major antitussive agent in most over-the-counter cough medicine. [15]

dextrorphan

Biologically active metabolite of dextromethorphan. [15]

5,7-DHT

See 5,7-dihydroxytryptamine. [6]

diacylglycerol (DAG)

Second messenger generated by the phosphoinositide second messenger system; stimulates protein kinase C (PKC). [3]

diazepam (Valium)

A BDZ that binds to the BDZ receptor, increasing the effectiveness of GABA to open the GABA_A receptor channel. [8]

diffusion tensor imaging (DTI)

An imaging technique that allows visualization of axonal connections and evaluates the integrity of the neuronal pathway. [4]

dihydro-beta-erythroidine (DhβE)

Blocks high-affinity nAChRs (i.e., receptors containing α4 and β2 subunits). [13]

5,7-dihydroxytryptamine (5,7-DHT)

Neurotoxin that selectively damages serotonergic neurons. [6]

1-(2,5-Dimethoxy-4-iodophenyl)-2-aminopropane (DOI)

Drug that stimulates 5-HT_2A receptors, producing “head-twitch” in rodents and hallucinations in humans. [6]

dimethyltryptamine (DMT)

Hallucinogenic drug found in several South American plants. [15]

Diprivan

See propofol. [8]

DISC1 gene

DISC1 variants may increase the probability of developing schizophrenia. [19]

disease model

Model of addiction that treats addiction as a distinct medical disorder or disease. [9]

dissociative anesthesia

An unusual type of anesthetic state characterized by environmental detachment. It is produced by certain noncompetitive NMDA receptor antagonists such as ketamine and PCP. [15]

disulfiram (Antabuse)

A drug used to treat alcoholism by causing the buildup of toxic metabolites producing illness after alcohol ingestion. [10]

divergence

Process by which neurons transmit their integrated signals back out to many neurons. [2]

dizocilpine

See MK-801. [8]

DMT

See dimethyltryptamine. [15]

DNA methylation

Environmentally-induced epigenetic covalent attachment of methyl groups to a gene decreases its expression. [2]

DNA microarray

Method used to screen tissue or cell extracts for changes in the expression of many genes at the same time. [19]

DOI

See 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane. [6]

domoic acid

Amino acid found in certain seafoods that causes excitotoxicity in organisms that consume it. [8]

donepezil (Aricept)

Drug that blocks AChE activity. It is used in the treatment of Alzheimer’s disease. [7]

dopamine (DA)

Neurotransmitter, related to NE and EPI, that belongs to a group called catecholamines. [5]

dopamine hypothesis of schizophrenia

Theory that altered DA function leads to the symptoms observed in individuals with schizophrenia. [19]

dopamine system stabilizers

Antipsychotic drugs that are DA partial agonists which increase DA function where it is too low and reduce DA function where it is excessive. [19]

dopamine β-hydroxylase (DBH)

Enzyme that catalyzes the third step of NE synthesis in neurons, the conversion of DA to NE. [5]

dopamine-deficient (DD) mouse

Mutant strain of mouse lacking dopamine from embryonic development onward. It is produced by genetically knocking out the tyrosine hydroxylase gene but restoring the gene in dopamine β-hydroxylase-expressing (i.e., noradrenergic) cells. [5]

dopaminergic

Adjectival form of dopamine. [5]

doping agents

Substances such as an anabolic steroids that are used to enhance athletic performance despite being banned by sports organizations. [16]

dorsal raphe nuclei

Structure located in the area of the caudal midbrain and rostral pons that contains a large number of serotonergic neurons. In conjunction with the median raphe nucleus, it is responsible for most of the serotonergic fibers in the forebrain. Together they regulate sleep, aggression, impulsiveness, and emotions. [2]

dorsal raphe nucleus

Structure located in the area of the caudal midbrain and rostral pons that contains a large number of serotonergic neurons. In conjunction with the median raphe nucleus, it is responsible for most of the serotonergic fibers in the forebrain. Together they regulate sleep, aggression, impulsiveness, and emotions. [6]

dorsal

Located toward the top of the brain and back of the body in humans. [2]

dose–response curve

Graph used to display the amount of biological change in relation to a given drug dose. [1]

double-blind experiment

Type of experiment in which neither the patient nor the observer knows the treatment received by the patient. [1]

down-regulation

Decrease in the number of receptors, which may be a consequence of chronic agonist treatment. [1]

DREADD

See chemogenetics. [4]

drug action

Molecular changes associated with a drug binding to a particular target site or receptor. [1]

drug competition

A factor that modifies biotransformation capacity. When two drugs share a metabolic system and compete for the same metabolic enzymes bioavailability of one or both increases. [1]

drug depots

Inactive sites where drugs accumulate. There is no biological effect from drugs binding at these sites, nor can they be metabolized. [1]

drug detoxification

Process whereby an individual eliminates a drug from the body and goes through an abstinence syndrome. [9]

drug disposition tolerance

See metabolic tolerance. [1]

drug effects

Alterations in physiological or psychological functions associated with a specific drug. [1]

drug priming

Delivery of a small dose of a drug by the experimenter for the purpose of eliciting drug-seeking behavior, typically in an animal whose drug self-administration responding was previously extinguished. See reinstatement of drug-seeking behavior. [9]

drug redistribution

Transfer of drug molecules from organs of high drug concentration to those of low concentration until equilibrium is reached in all tissues. [1]

drug reward

A positively-motivating subjective response to a drug, often experienced by humans as a euphoric feeling or “high.” [9]

drug-seeking behavior

Performance of an operant response such as a lever-press or a nose-poke with the expectation of receiving delivery of a drug dose. [12]

dry mouth effect

Lack of salivation that is a side effect of drugs with muscarinic receptor blocking activity. [7]

DTs

See delerium tremens. [10]

dual NE/5-HT modulators

Antidepressants that enhance both NE and 5-HT function. [18]

dura mater

The outer layer of the meninges. It is the strongest of the three meninges layers. [2]

dyskinesias

Abnormal or impaired movement such as severe tics or choreic movements. [20]

dystonia

Persistent invuluntary muscle contractions. [20]

E

EAATs

See excitatory amino acid transporters. [8]

early LTP (E-LTP)

Type of long-term potentiation that lasts no longer than a few hours. [8]

Edronax

See reboxetine. [5]

EEG

See electroencephalography. [4]

effector enzymes

Enzymes of the cell membrane that may be regulated by G proteins and that cause biochemical and physiological effects in postsynaptic cells (e.g., by means of second messengers). [3]

efficacy

The extent to which a ligand-receptor binding initiates a biological action (e.g., the ability of an agonist to activate its receptor). [1]

Eldepryl

See selegiline. [5]

electrical self-stimulation

A procedure whereby an animal self-administers a weak electrical shock to a specific brain area due to the reinforcing properties of the stimulation. [4, 9]

electroencephalography (EEG)

Technique used to measure brain activity by using electrodes taped on the scalp to obtain electrical recordings in humans. [4]

electrostatic pressure

Force drawing an ion to either side of the cell membrane in an attempt to balance or neutralize ionic charges. [2]

elevated plus-maze

Maze type that involves a cross-shaped maze that has two open arms, two enclosed arms, and has been raised 50 cm off the floor. It is used to test a rodent’s level of anxiety. [4]

endocannabinoid membrane transporter

Hypothesized membrane carrier protein that binds anandamide and transports it into the cell. [14]

endocannabinoids

Lipid-like substances that activate CB receptors. They are produced from arachidonic acid in the body. [14]

endocrine glands

Specialized organs that secrete hormones into the bloodstream. [3]

endomorphins

Group of endogenous opioid peptides in the CNS that selectively bind to the opioid receptor, and eliminate pain. [11]

endorphins

Group of endogneous peptides in the brain that stimulate mu and delta opioid receptors, reducing pain and enhancing one’s general mood. [11]

endosomes

Membranous structures present in axon terminals that play a role in one type of vesicle recycling. [3]

entacapone (Comtan)

COMT inhibitor used in conjunction with l-DOPA to treat Parkinson’s disease. [5]

enteral

Drug administration by oral or rectal routes. [1]

enteric nervous system

Large system of ganglia located in the muscle walls of the intestines. Some of the neurons within this system use 5-HT as a neurotransmitter. [6]

enterochromaffin cells

Specialized secretory cells within the walls of the intestines that synthesize and secrete 5-HT. [6]

enzyme induction

Increase in liver drug-metabolizing enzymes associated with repeated drug use, which leads to drug tolerance. [1]

enzyme inhibition

In drug metabolism, reduction in liver enzyme activity associated with a specific drug may cause more intense or prolonged effects of other drugs taken at the same time. [1]

enzyme-linked immunosorbent assay (ELISA)

An immunoassay used to quantify a specific protein that does not rely on radioactivity for detection but instead uses a colored reaction product. [4]

ephedrine

Psychostimulant that is a constituent of the herb Ephedra vulgaris. [12]

EPI

See epinephrine. [3, 5]

epidural

Method that involves administration of a drug into the cerebrospinal fluid surrounding the spinal cord. [1]

epinephrine (EPI)

Hormone related to NE that belongs to a group called catecholamines. It is secreted by the chromaffin cells of the adrenal medulla, and it produces the “fight-or-flight” response by regulating the diversion of energy and blood to muscles. Also known as adrenaline. [3, 5]

EPSP

See excitatory postsynaptic potential. [2]

equilibrium potential for potassium

Point at which the electrostatic pressure and the concentration gradient for potassium are balanced. [2]

ergot

Fungus, Claviceps purpurea, that infects certain grains and that contains several important alkaloids from which the structure of LSD was derived. [15]

ergotism

Disease caused by ergot-contaminated grains that can lead to death. [15]

ERK

Extracellular signal-regulated kinase, a major component of the MAP kinase system. [3]

eserine

See physostigmine. [7]

estradiol

Specific estrogen and a powerful female sex hormone. [3]

estrogens

Female sex hormones secreted by the ovaries. [3]

ethanol

Proper chemical name for the type of alcohol consumed by humans. Similar to BDZs, it acts as a CNS-depressant in part by enhancing GABA_A receptor activity. [8]

event-related potentials (ERPs)

Electrical changes in neuron activity in response to a sensory stimulus. [4]

excitatory amino acid neurotransmitters

Transmitters, including glutamate, aspartate, and some other amino acids, that cause an excitatory response in most neurons of the brain or spinal cord. [8]

excitatory amino acid transporters (EAATs)

Protein that transports glutamate and aspartate across the plasma membrane. There are five such transporters, designated EAAT1 to EAAT5. [8]

excitatory postsynaptic potentials (EPSPs)

Small localized membrane depolarizations of a postsynaptic neuron that result from neurotransmitters binding to specific receptors that open ion channels. EPSPs move the membrane potential closer to the threshold for firing. [2]

excitotoxicity hypothesis

Theory that excessive glutamate or other excitatory amino acid exposure results in prolonged depolarization of receptive neurons, leading to their damage or death. [8]

executive function

Collection of higher-order cognitive abilities including planning, organization, problem solving, mental flexibility, and valuation of incentives. The prefrontal cortex plays an important role in executive function. [9]

exocytosis

Method by which vesicles release substances and neurotransmitters, characterized by fusion of the vesicle and the cell membrane, specifically the axon terminal membrane in the case of neurotransmitters. The vesicle opens toward the synaptic cleft allowing neurotransmitter molecules to diffuse out. [3]

expectancy

Term used to describe the anticipated effect of a drug and its role in drug action or perceived drug action. [10]

expression phase

The period of time after a tetanic stimulation is given, characterized by enhanced synaptic strength (i.e., LTP). [8]

expression

Process that leads to manifestation of a sensitized response and that requires enhanced reactivity of DA nerve terminals in the nucleus accumbens. [12]

extracellular fluid

Salty fluid surrounding nerve cells that provides oxygen, nutrients, and chemical signals, and that removes secreted cell waste. [2]

extracellular recording

Method of taking measurements of cell firing by inserting a fine-tipped electrode into the extracellular fluid surrounding the cell. [4]

F

face validity

Term used to describe the relationship between a testing procedure done on animals and its direct correlation to human test results or behavior. [4]

FAS

See fetal alcohol syndrome. [10]

FASD

See fetal alcohol spectrum disorder. [10]

fatigue

State of weariness that diminishes an individual’s energy and mental capacity. [20]

fatty acid amide hydrolase (FAAH)

Enzyme that metabolizes endocannabinoids. [14]

fatty liver

Damaging effect of alcohol characterized by the accumulation of triglycerides inside liver cells. [10]

fear-potentiated startle

Enhancement of a startle response when the stimulus is preceded by the presentation of a conditioned fear stimulus. [4]

fenestrations

Large pores in endothelial cells allowing rapid exchange of materials between blood vessels and tissue. [1]

fenfluramine

Drug similar in structure to amphetamine that stimulates 5-HT release. It is an appetite suppressor formerly used as a treatment for obesity. [6]

festination

Uncontrollable acceleration of gait. [20]

fetal alcohol spectrum disorders (FASD)

A cluster of disorders due to developmental abnormalities caused by prenatal exposure to alcohol. Features vary but may include learning disabilities, poor impulse control, and attention deficits. [10]

fetal alcohol syndrome (FAS)

The damaging developmental effects of prenatal alcohol exposure. [10]

fetal solvent syndrome

Group of symptoms, typically including cognitive deficits and craniofacial (i.e., head and face) abnormalities, seen in some newborn infants of inhalant-abusing women. [16]

first-order kinetics

Term used to describe exponential elimination of drugs from the bloodstream. [1]

first-pass metabolism

Phenomenon in which the liver metabolizes some of a drug before it can circulate through the body, particularly when the drug has been taken orally. [1]

fissures

Deep grooves of the cerebral cortex. [2]

flashbacks

Reexperience of the perceptual drug effects, specifically those of a hallucinogen, following termination of drug use. [15]

fluoxetine (Prozac)

Drug that selectively blocks the 5-HT transporter. It is used as an antidepressant. [6]

fMRI

See functional MRI. [4]

focused stereotypies

Behaviors produced by high doses of psychostimulants (e.g., cocaine and amphetamine) and characterized by repetitive and aimless movement. [12]

follicle-stimulating hormone (FSH)

Hormone secreted by the anterior pituitary that helps control gonad growth and function. [3]

forced swim test

Technique used to measure depression in animals by placing them in a cylinder of water from which they cannot escape and recording the time it takes for them to abandon attempts to escape. [4]

fragile X mental retardation 1 gene (FMR1)

Gene that codes for the fragile X mental retardation protein (FMRP). [8]

fragile X mental retardation protein (FMRP)

Protein encoded by the FMR1 gene that regulates local protein synthesis at postsynaptic sites. Deficiency of FMRP due to FMR1 mutations is the cause of fragile X syndrome. [8]

fragile X syndrome

Congenital disorder that is a leading cause of intellectual disability and autistic symptoms. It is caused by a mutation in the fragile X mental retardation 1 gene (FMR1). [8]

freebasing

Smoking the freebase form of cocaine obtained by dissolving cocaine HCl in water, adding an alkaline solution, and then extracting with an organic solvent. [12]

frontal

Tissue sections cut parallel to the face. [2]

frontal lobe

One of four lobes of the cerebral cortex. It is responsible for movement and executive planning. [2]

FSH

See follicle-stimulating hormone. [3]

fuels

Class of inhalants composed of volatile liquids or gases that serve many purposes, including automobile fuel, fuels for lamps and heating appliances, lighter fluids, and propellants used in many kinds of spray cans. [16]

functional MRI (fMRI)

Technique used to regionally visualize brain activity by detecting the increase in blood oxygen levels through magnetic resonance measurements of oxygenated and oxygen-depleted hemoglobin. [4]

G

G protein–coupled receptor

Slow acting receptor type composed of a single large protein in the cell membrane that activates G proteins. It may also be called a metabotropic receptor. [3]

G proteins

Specific membrane proteins that are necessary for neurotransmitter signaling by metabotropic receptors. They operate by regulating ion channels or effector enzymes involved in the synthesis or breakdown of second messengers, ultimately causing biochemical or physiological changes in the postsynaptic cell. [3]

GABA

See γ-aminobutyric acid. [8]

GABA aminotransferase (GABA-T)

Enzyme that breaks down GABA in GABAergic neurons and astrocytes. [8]

GABA_A receptor

Ionotropic receptor for GABA that allows Cl^– ions to enter the cell, thereby inhibiting cell firing. [8]

GABAB receptor

Metabotropic receptor for GABA. [8]

Gabitril

See tiagabine. [8]

GAD

See generalized anxiety disorder or glutamic acid decarboxylase. [8, 17]

gait

Pattern of limb movement during locomotion over a solid surface. [4]

galantamine (Reminyl)

Drug that blocks AChE activity. It is used in the treatment of Alzheimer’s disease. [7]

γ-aminobutyric acid (GABA)

Amino acid that is the principal inhibitory neurotransmitter in the CNS. [8]

γ-hydroxybutyrate (GHB)

Chemical similar in structure to GABA that produces sedative and anesthetic effects in users and that is used medicinally as well as recreationally. [16]

ganglia

A cluster of cell bodies outside the CNS. [2]

gaseous transmitters

Substances in the gas phase that acts as neurotransmitters in the body. [3]

GAT-1

Member of the family of plasma membrane GABA transporters that is expressed in both neurons and astrocytes. [8]

GAT-2

Member of the family of plasma membrane GABA transporters that is expressed in both neurons and astrocytes. [8]

GAT-3

Member of the family of plasma membrane GABA transporters that is expressed only in astrocytes. [8]

gated channels

Ion channels that are normally in a closed configuration that can be opened momentarily by specific stimuli. [2]

gateway theory

Theory proposing that use of certain drugs of abuse, particularly during childhood or adolescence, increases the risk of progressing to other substances. For example, tobacco or alcohol have been proposed as gateways to marijuana use, and in turn marijuana has been proposed as a gateway to so-called “hard drugs” like cocaine or heroin. [9]

gene therapy

Application of DNA that encodes a specific protein to increase or block expression of the gene product to correct a clinical condition. [1]

generalized anxiety disorder (GAD)

An anxiety disorder characterized by excessive worrying that does not have a specific cause. [17]

genes

Portions of a chromosome that code for particular proteins. [2]

genetic models

Creation of knockout, knockin, or transgenic mice to produce a phenotype analagous to the human clinical disorder of interest. [19]

genetic polymorphisms

Genetic variations in a population resulting in multiple forms of a particular protein. [1]

genome-wide association studies (GWAS)

A modification of microarray technology used to compare the incidence of single-nucleotide polymorphisms and copy number variants in DNA samples from people with a given disorder and matched controls. [4, 9, 10]

GH

See growth hormone. [3]

GHB

See γ-hydroxybutyrate. [16]

glial cells

Supporting cells of the nervous system that insulate, protect, and metabolically support neurons. [2]

gliotransmission

Chemical transmission mediated by transmitter release from glial cells such as astrocytes. [8]

glucagon

Hormone secreted by the islets of Langerhans that, along with insulin, regulates metabolic energy sources in the body. [3]

glucocorticoid hypothesis

Theory that stress-induced elevation of glucocorticoid levels accelerate cell damage including decreases in dendritic branches and loss of dendritic spines and apoptosis in multiple brain regions, and failure of neurogenesis in the hippocampus and leads to the symptoms of depression. [18]

glucocorticoids

Hormones belonging to the steroid family that are secreted by the adrenal cortex and help maintain blood glucose levels in the body. [3]

glutamate

The ionized form of glutamic acid. It is an excitatory amino acid neurotransmitter of the CNS. [8]

glutamatergic neurons

Neurons that use glutamate as a transmitter. [8]

glutamic acid decarboxylase (GAD)

Enzyme that transforms glutamate into GABA. [8]

glutaminase

Enzyme that transforms glutamine into glutamate. [8]

glutamine

Precursor of the transmitter-related glutamate. [8]

glutamine synthetase

Enzyme in astrocytes that converts glutamate into glutamine. [8]

glycine

Amino acid characterized by the lack of a functional group. It is a co-agonist with glutamate for the NMDA receptor. [8]

GnRH

See gonadotropin-releasing hormone. [3]

gonadotropin-releasing hormone (GnRH)

Hormone that stimulates FSH and LH release. It is synthesized by neurons of the hypothalamus. [3]

gonads

Glands that secrete sex-specific steroid hormones. [3]

granisetron (Kytril)

Drug that inhibits 5-HT₃ receptors. It is used to treat the nausea and vomiting side effects of cancer chemotherapy. [6]

growth hormone (GH)

Hormone secreted by the anterior pituitary that increases production of IGF-I in peripheral organs. [3]

guanfacine

α_2A-adrenergic agonist prescribed for the treatment of ADHD. Guanfacine is believed to improve attention and memory by stimulating α_2A-adrenergic receptors in the prefrontal cortex. [5]

GWAS

See genome-wide association studies. [4, 9, 10]

gyri (sing. gyrus)

Bulges of tissue between the grooves in the cerebral cortex. [2]

H

half-life

Time required to remove half of the drug from the blood. It is referred to as t_1/2. [1]

hallucinogen persisting perception disorder (HPPD)

Disorder of hallucinogen use characterized by severe perceptual symptoms (i.e., flashbacks) that persist for a long period of time following drug use and are experienced sufficiently frequently to cause significant distress or impairment to the individual. [15]

hallucinogen rating scale

Psychometric scale developed to quantify the subjective effects of hallucinogenic agents. [15]

hallucinogenic

Adjectival form of hallucinogen. [6, 15]

halogenated hydrocarbons

Class of inhalants composed of hydrocarbon molecules possessing one or more chlorine or fluorine atoms. [16]

haloperidol

A D₂ receptor blocker that can induce catalepsy in animals when administered in high doses. It is used clinically as an antipsychotic agent. [5]

hangover

Effect of heavy alcohol consumption that may be a sign of withdrawal, acute toxicity, or other negative effects on body regulation. [10]

hashish

Type of cannabis derivative that is smoked or eaten. [14]

HD

See Huntington’s disease. [20]

hemicholinium-3 (HC-3)

Drug that blocks the choline transporter in cholinergic nerve terminals. [7]

heritability

The relative contribution of genetics to the variability of a trait within a population. [9]

heteroreceptors

Axon receptors that are specific for neurotransmitters released by other cells at axoaxonic synapses. They may either decrease or increase further neurotransmitter release. [3]

5-HIAA

See 5-hydroxyindoleacetic acid. [6]

hippocampus

Subcortical structure of the limbic system that helps to establish long-term, contextual, and spatial memories. The hippocampus is where LTP was first discovered and is also one of the brain areas damaged in Alzheimer’s disease. [2]

homovanillic acid (HVA)

Major metabolite formed in the breakdown of DA. [5]

horizontal

Brain sections cut parallel to the horizon. [2]

hormones

Chemical substances secreted by endocrine glands into the bloodstream, where they travel to target locations in the body. [3]

hot plate test

Method used to evaluate analgesia by subjecting an animal to a heated metal plate and measuring the time it takes to make an avoidance response. [4]

5-HT

See serotonin. [6]

5-HT transporter (SERT)

Protein in the membrane that is responsible for 5-HT reuptake from the synaptic cleft. [6]

5-HTP

See 5-hydroxytryptophan. [6]

huntingtin gene

Gene containing a CAG trinucleotide repeat. A mutation resulting in more than 40 repeats of the CAG sequence results in Huntington’s disease. [20]

Huntington’s chorea

Involuntary jerky, writhing movements of the limbs. [20]

Huntington’s disease (HD)

An inherited disorder caused by a genetic defect on chromosome 4. The defect results in the abnormal repetition of a CAG sequence. The disorder causes progressive degeneration of nerve cells in the brain resulting in movement, cognitive, and psychiatric symptoms. [20]

HVA

See homovanillic acid. [5]

5-hydroxyindoleacetic acid (5-HIAA)

Major metabolite of 5-HT that is produced by the action of MAO. [6]

6-hydroxydopamine (6-OHDA)

Neurotoxin similar in structure to DA that damages catecholaminergic nerve terminals and is used to study catecholamine pathways. [5, 20]

2-hydroxysaclofen

Chemical analog of baclofen that is a competitive antagonist at the GABA_B receptor. [8]

5-hydroxytryptamine (5-HT)

Neurotransmitter present in the central and peripheral nervous system and synthesized by the serotonergic neurons. Also known as serotonin. [6]

5-hydroxytryptophan (5-HTP)

Intermediate formed in the synthesis of 5-HT. [6]

8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT)

Drug that stimulates 5-HT_1A receptors. Effects include increased appetite, reduced anxiety, reduced alcohol cravings, and a lower body temperature. [6]

hyperalgesia

Condition characterized by an increased sensitivity to pain. [6, 14]

hypercapnia

Elevated blood CO₂ levels. [6]

hyperpolarization

Change in membrane potential making the inside of a cell more negative relative to the resting potential, reducing the likelihood that the cell will fire an action potential. [2]

hypnagogic hallucinations

Vivid dreamlike sensations that occur during the daytime in some patients with narcolepsy. [3]

hypnotics

Drugs, such as benzodiazepines, that help a patient to fall asleep and stay asleep. [17]

hypocretin 1

See orexin-A. [3]

hypocretin 2

See orexin-B. [3]

hypoglutamate model

NMDA antagonists produce rodent behaviors analogous to the positive, negative, and cognitive symptoms of schizophrenia. [19]

hypophagia

Decrease in food consumption due to loss of appetite. [6]

hypothalamic releasing hormones

Neuropeptide hormones synthesized by neurons of the hypothalamus and carried by blood vessels to the anterior pituitary, where they control the release of many of the pituitary hormones. [3]

hypothalamus

Structure of the diencephalon located at the base of the brain, ventral to the thalamus. It provides many functions important for survival, including the maintenance of body temperature and salt balance, regulation of hunger and thirst, control of the ANS and pituitary gland, and modulation of emotional responses. [2]

I

idalopirdine

Drug that inhibits 5-HT₆ receptors. It has been tested for treating cognitive decline in patients with Alzheimer’s disease. [6]

192 IgG–saporin

Neurotoxin containing the monoclonal antibody 192 IgG, which binds to cholinergic neurons in the forebrain, and the cellular toxin saporin. It is used to selectively kill cholinergic neurons. [7]

IM

See intramuscular. [1]

immunocytochemistry (ICC)

Technique that uses antibodies to determine the brain areas or neurons that contain a specific antigen such as a protein, neuropeptide, or neurotransmitter. [4]

in situ hybridization (ISH)

Technique used to locate cells that manufacture a specific protein or peptide by detecting the specific mRNA sequence coding for that substance. It can also be used to study changes in regional mRNA levels (i.e., gene expression). [4]

in vitro

Refers to measurements performed outside the living body (traditionally in a test tube). [4]

in vivo

Refers to measurements observed in the living organism. [4]

in vivo voltammetry

Technique used to measure neurotransmitter release in the brain of an awake, freely moving animal by using a microelectrode to measure electrochemical responses to an applied electrical signal. [4]

25I-NBOMe

Member of the NBOMe class of hallucinogens containing an iodine atom attached to the phenyl ring. [15]

incentive salience

Psychological process by which drug-related stimuli gain increased prominence and attractiveness. It is an important component of the incentive-sensitization model of addiction. [9]

incentive sensitization theory

Model of addiction based on the theory that repeated drug use leads to an increase in “wanting” the drug (i.e., craving) but no increase in drug “liking” (reward or euphoria) because only the neural system underlying drug “wanting” becomes sensitized. [9]

incubation

Time-dependent increase in drug craving and drug seeking behavior during abstinence. [12]

Inderal

See propranolol. [5]

indoleamine

Indole derivative containing an amine group. Indoleamines include serotonin and the hallucinogens LSD, psilocybin, psilocin, DMT, and 5-MeO-DMT. [15]

induction

1. Increase in liver enzymes specific for drug metabolism in response to repeated drug use. 2. Process that establishes psychostimulant sensitization by activating glutamate NMDA receptors and, in some cases, D₁ receptors. [10, 12]

induction phase

Phase of LTP, during and immediately after a tetanic stimulation is given, which requires activation of NMDA receptors. [8]

inferior

Located toward the underside of the brain in humans. [2]

infusion pump

Drug delivery via an implanted pump (e.g., subcutaneous) that delivers regular, constant doses to the body or into the cerebral ventricles. [1]

inhalants

Group of volatile substances, such as glue, that may be abused as a drug by inhaling the fumes. [16]

inhalation

Method that involves administration of a drug through the lungs. [1]

inhibitory postsynaptic potentials (IPSPs)

Hyperpolarizing responses of a postsynaptic cell that result from neurotransmitters opening ion channels. [2]

inositol trisphosphate (IP₃)

See diacylglycerol (DAG). [3]

insulin

Polypeptide hormone that is secreted by the islets of Langerhans and, along with glucagon, regulates glucose and metabolic energy sources in the body. It regulates glucose uptake from the bloodstream into tissues and stimulates the uptake of certain amino acids. [3, 6]

integration

Process at the axon hillock whereby several small depolarizations or hyperpolarizations will summate to create a larger change in membrane potential. Similarly, simultaneous depolarizations and hyperpolarizations will cancel each other out. [2]

intercellular clefts

Small gaps between adjacent cells. These gaps between endothelial cells of typical blood vessels permit the passage of molecules to and from the blood. [1]

Interferon beta 1a

Drug used in the treatment of relapsing forms of MS. [20]

Interferon beta 1b

Drug used in the treatment of relapsing forms of MS. [20]

interictal period

Time interval between seizures in an epileptic patient. [8]

interneurons

Nerve cells in the CNS and spinal cord that form complex neural circuits providing sensorimotor integration. [2]

intracellular recording

Method of taking measurements of cell firing by inserting a fine-tipped electrode into the cell. [4]

intracerebroventricular

Method that involves administration of a drug into the cerebrospinal fluid of the ventricles. [1]

intracranial

Method that involves administration of a drug into the brain tissue. [1]

intramuscular (IM)

Method that involves administration of a drug by injection into a muscle. [1]

intranasal administration

Topical administration of a drug to the nasal mucosa. [1]

intraperitoneal (IP)

Injection technique that is the most common route of administration for small laboratory animals. The drug is injected through the abdominal wall into the peritoneal cavity—the space that surrounds the abdominal organs. [1]

intrauterine growth restriction (IUGR)

Condition in which fetal growth is hampered, thereby resulting in a baby being born underweight for its gestational age. [13]

intravenous (IV)

Method that involves administration of a drug directly into the bloodstream by means of injection into a vein. [1]

inverse agonists

Substances that activate a receptor but produce the opposite effect of typical agonists at that receptor. [1, 8]

Inversine

See mecamylamine. [7]

ionization

Process involving the dissociation of an electrically neutral molecule into charged particles (ions). [1]

ionotropic receptor

Fast acting receptor type comprised of several subunits that come together in the cell membrane. The receptor has an ion channel at its center, which is regulated by neurotransmitters binding to specific sites on the receptor causing the channel to open. It may also be called a ligand-gated channel receptor. [3]

iontophoresis

Process by which electrically charged drug molecules stored in a reservoir inside a skin patch are driven into the skin by the passage of electrical current. This process can be used for constant administration of migraine headache medications. [6]

IP

See intraperitoneal. [1]

ipsapirone

Drug that stimulates 5-HT_1A receptors. Some of its effects include increased appetite, reduced anxiety, reduced alcohol cravings, and a lower body temperature. [6]

IPSP

See inhibitory postsynaptic potential. [2]

irritable bowel syndrome (IBS)

Gastrointestinal disorder characterized by abdominal pain, gas and bloating, frequent abnormal bowel movements (diarrhea, constipation, or an alternation between the two), and mucus in the stool. [6]

ischemia

Condition characterized by an interruption of blood flow to the brain. [8]

ISH

See in situ hybridization. [4]

islets of Langerhans

Endocrine gland in the pancreas that secretes insulin and glucagons. [3]

isoproterenol

β-adrenergic receptor agonist. [5]

IUGR

See intrauterine growth restriction. [13]

IV

See intravenous. [1]

J

John Cunningham (JC) virus

Common virus that is present in more than 50% of the population. Most people acquire it sometime during childhood. It lives in a latent harmless state in the kidneys and the gastrointestinal tract in individuals with healthy immune systems, but becomes life-threatening in those whose immune systems are compromised. The virus causes progressive multifocal leukoencephalopathy (PML), a rare, but frequently deadly condition that destroys myelin, a protective covering of nerve cells in the brain. [20]

K

kainate receptor

An ionotropic glutamate receptor selective for the agonist kainic acid. [8]

κ-receptors

An opioid receptor located in the striatum, amygdala, hypothalamus, and pituitary gland that may help regulate pain, perception, gut motility, dysphoria, water balance, hunger, temperature, and neuroendocrine function. [11]

ketamine

Drug that binds to the PCP site and acts as a noncompetitive antagonist of the NMDA receptor. It is a dissociative anesthetic used in both human and veterinary medicine, and it is also used recreationally. [8, 15]

ketanserin

Drug that inhibits 5-HT_2A receptors. [6]

kiss-and-run

Hypothesized type of exocytosis in which the synaptic vesicle does not collapse during the neurotransmitter release process, thus eliminating the need for an endocytotic mechanism to retrieve vesicle membrane components from the membrane of the axon terminals. [3]

knockin mice

Mice that have a specific gene inserted into their DNA, so they produce a slightly different protein than is produced by wild-type mice. [4]

knockout mice

Mice that are homozygous for the targeted deletion of a specific gene. They are used to study the normal function of that gene as well as the involvement of the gene in behavioral and physiological responses to various psychoactive drugs. [4]

L

l-2-amino-4-phosphonobutyrate (l-AP4)

Synthetic amino acid that is an agonist selective for glutamate autoreceptors. [8]

l-DOPA

Precursor necessary for the synthesis of DA. l-DOPA is formed by the addition of a hydroxyl group to tyrosine by the enzyme TH. It is used to treat Parkinson’s disease by increasing DA formation. [5]

l-DOPA

Precursor necessary for the synthesis of DA. l-DOPA is formed by the addition of a hydroxyl group to tyrosine by the enzyme TH. It is used to treat Parkinson’s disease by increasing DA formation. [20]

late LTP (L-LTP)

Type of LTP that is dependent on protein synthesis and that can last for much longer periods of time than early LTP. [8]

lateral

Located to either side of the body or brain. [2]

laterodorsal tegmental nuclei (LDTg)

Structure within the dorsal lateral pons containing cholinergic neurons that project to the ventral tegmental area (important for stimulating VTA dopamine neurons) and others that project to the brainstem and thalamus (important for behavioral arousal, sensory processing, and inititation of rapid-eye-movement sleep). [7]

LC

See locus coeruleus. [5]

LDTg

See laterodorsal tegmental nucleus. [7]

learned helplessness

A classic screening device for antidepressant drugs. After being subjected to periods of unescapable foot shock, rodents fail to respond when given the opportunity to alter an aversive event. Antidepressant drugs increase appropriate responding.

lesioning

Process whereby brain cells are destroyed using an electrode to administer a high radio frequency current, or by injecting a neurotoxin that kills cells. [4]

Levodopa

See l-DOPA.

Lewy body dementia (LBD)

Progressive form of dementia that is similar in symptomology to Parkinson’s disease and Alzheimer’s disease. Characterized by abnormal accumulations of proteins (Lewy bodies) in the nuclei of neurons in the brain that control memory and movement. [20]

Lewy body

An abnormal aggregate of protein that develop inside neurons in Parkinson’s disease and Lewy Body dementia. [20]

LH

See luteinizing hormone. [3]

ligand-gated channel receptors

See ionotropic receptor. [3]

ligand-gated channels

Types of ion channels that are regulated by a ligand binding to a receptor site associated with the particular channel. [2]

ligand

Molecule that selectively binds to a receptor. [1]

light–dark crossing task

Test used to determine a rodent’s level of anxiety by placing it in a two-compartment box, one side lit and the other side dark. Fewer crossings and less time spent in the lighted side indicate anxiety. [4]

limbic system

Neural network that integrates emotional responses and regulates motivated behavior, reinforcement, and learning. Some major structures include the limbic cortex, amygdala, nucleus accumbens, and hippocampus. [2]

linkage analysis

Genetic method that seeks to find chromosomal regions that tend to associate with a disorder (e.g., a substance-related disorder) that is being studied. [9]

linkage studies

Methods used to locate genes responsible for a disorder, such as alcohol use disorder or schizophrenia, by comparing similarities in the genetic loci of families with affected members. [18]

Lioresal

See baclofen. [8]

lipids

Fatty molecules in the body. Lipids are a major component of cell membranes, and some of them also act as neurotransmitters. [3]

lithium carbonate

Drug that stabilizes moods, preventing episodes of mania and depression, in people with bipolar disorder. [18]

local potentials

Small localized short-lived change in voltage across the cell membrane following the opening of ligand-gated channels. [2]

loci (sing. locus)

The location of genes on a chromosome. [19]

locus coeruleus (LC)

Collection of noradrenergic neurons in the reticular formation of the pons that supplies most of the NE to the cortex, limbic system, thalamus, and hypothalamus. These cells cause arousal and increased attention when active. [2, 5]

long-term depression (LTD)

Type of synaptic plasticity resulting in weakening of synaptic connections. [8]

long-term potentiation (LTP)

Phenomenon whereby synaptic connections are strengthened for a period of at least an hour. It requires activation of NMDA receptors for its induction and AMPA receptors for its expression. [8]

Lopressor

See metoprolol. [5]

lorcaserin (Belviq)

Drug that selectively stimulates 5-HT_2C receptors. It is used in the treatment of obesity. [6]

LSD

See lysergic acid diethylamide. [6, 15]

LTD

See long-term depression. [8]

LTP

See long-term potentiation. [8]

luteinizing hormone (LH)

Hormone secreted by the anterior pituitary that helps control gonad growth and function, and increases estrogen and androgen secretion. [3]

lysergic acid

Core structural unit of all ergot alkaloids. [15]

lysergic acid diethylamide (LSD)

Hallucinogenic drug that is synthesized from lysergic acid and based on alkaloids found in ergot fungus. It is thought to produce its effects mainly by stimulating 5-HT_2A receptors in the brain. [6, 15]

lysis

Bursting of a cell. [8]

M

macroelectrode

Device used to electrically stimulate deep brain regions while monitoring behavior or recording the summated electrical response of thousands of neurons. [4]

MAGL

See monoacylglycerol lipase. [14]

magnetic resonance imaging (MRI)

Technique used to visualize in high resolution, detailed slices through the brain or other organ by taking computerized measurements of the signals emitted by atoms in the tissue as they are exposed to a strong magnetic field. Computer technology permits recreation of the structure in 3-dimensions. [4]

magnetic resonance spectroscopy (MRS)

Using MRI-generated data, MRS calculates the quantity of brain chemicals such as glutamate. [4]

magnetogenetics

Genetic manipulations that make cells sensitive to magnets. Remote magnetic stimulation of specific cells is used to trigger a behavioral response. [4]

major depression

Type of affective disorder characterized by extreme recurring episodes of dysphoria and negative thinking that are reflected in behavior. [18]

male hypogonadism

Condition involving deficient functioning of the testes, abnormally low secretion of testosterone, and reduced sperm production. [16]

MAO inhibitors (MAOIs)

Class of drugs that inhibit monoamine oxidase (MAO), thereby causing an accumulation of catecholamines and serotonin in the brain. They are often used to treat clinical depression. [5, 18]

MAO

See monoamine oxidase. [5]

MAP kinase system

Family of mitogen-activated protein kinases known to play important roles in growth, development, and synaptic plasticity. [3]

marijuana

Crude mixture of dried and crumbled leaves, small stems, and flowering tops of the cannabis plant. [14]

maternal separation

Technique used to test the role of early-life stress as a factor in the development of depression, substance abuse, and other psychopathology. Week-old animals are separated from their mothers for brief periods daily. [4]

mavoglurant

Selective mGluR5 antagonist that was developed and clinically tested for the treatment of fragile X syndrome. [8]

MDMA

See 3,4-methylenedioxymethamphetamine. [6]

MDPV

Cathinone derivative (3,4-methylenedioxypyrovalerone) that is an abused stimulant drug. It is a member of a group of compounds sometimes called “bath salts,” “plant food,” “pond water cleaner,” and “legal highs.” [12]

mecamylamine (Inversine)

Drug that is an antagonist for nicotinic ACh receptors. [7, 13]

medial

Located near the center or midline of the body or brain. [2]

median eminence

Area in the hypothalamus that is not isolated from chemicals in the blood and where hypothalamic-releasing hormones are secreted for transport to the anterior pituitary gland. [3]

median raphe nuclei (sing. nucleus)

Structure located in the area of the caudal midbrain and rostral pons that contains a large number of serotonergic neurons. In conjunction with the dorsal raphe nucleus, it is responsible for most of the serotonergic fibers in the forebrain. Together they regulate sleep, aggression, impulsiveness, and emotions. [2, 6]

medical model

See disease model. [9]

medulla

Structure located in the caudal brain stem responsible for regulating heart rate, digestion, respiration, blood pressure, coughing, and vomiting. [2]

melatonin

Hormone that regulates rhythmic functions in the body. It is secreted by the pineal gland. [3]

memantine (Namenda)

Noncompetitive NMDA receptor antagonist that is used to treat moderate to severe Alzheimer’s disease. [8, 20]

meninges

Layers of protective tissue located between the bones of the skull and vertebrae and the tissue of the brain and spinal cord. [2]

MEOS

See microsomal ethanol oxidizing system. [10]

mephedrone

Cathinone derivative (4-methylmethcathinone) that is an abused stimulant drug. It is a member of a group of compounds sometimes called “bath salts,” “plant food,” “pond water cleaner,” and “legal highs.” [12]

3-mercaptopropionic acid

Drug that blocks GABA synthesis, inducing convulsions. [8]

mescal button

Crown of the peyote cactus, Lophophora williamsii, which can be dried and ingested to obtain the hallucinogenic drug mescaline. [15]

mescaline

Hallucinogenic drug produced by several cacti species, especially that of the peyote cactus, Lophophora williamsii. [15]

mesocortical dopamine pathway

Group of dopaminergic axons that originates in the VTA and travels to the cerebral cortex, including the prefrontal, cingulated, and entorhinal cortices. It may also be called the mesocortical tract. [5]

mesolimbic dopamine pathway

Group of dopaminergic axons that originates in the VTA and travels to structures of the limbic system, including the nucleus accumbens, septum, amygdala, and hippocampus. It may also be called the mesolimbic tract. [5]

Mestinon

See pyridostigmine. [7]

metabolic tolerance

Type of tolerance to a drug that is characterized by a reduced amount of drug available at the target tissue, often as a result of more-rapid drug metabolism. It is sometimes also called drug disposition tolerance. [1, 10]

metabolites

Byproducts of biochemical pathways, such as those involved in neurotransmitter or drug inactivation. [5]

metabotropic glutamate receptor theory

Theory that loss of FMRP causes exaggerated group I mGluR-related functions, which results in the characteristic of fragile X syndrome. [8]

metabotropic receptor

Slow-acting receptor type composed of a single large protein in the cell membrane that activates G proteins. It may also be called a G protein–coupled receptor. [3]

methadone

A long-acting opioid drug that may be substituted for other opioids in order to prevent withdrawal symptoms. [11]

methadone maintenance program

Most effective treatment program for opioid addicts that involves the substitution of the opioid with methadone to prevent withdrawal symptoms and craving to avoid a relapse. [11]

methamphetamine

Psychostimulant that acts by increasing catecholamine release from nerve terminals. It can also cause neurotoxicity at high doses. [5, 12]

methoxetamine

Potent ketamine analog that is an abused drug. [15]

5-methoxy-dimethyltryptamine (5-MeO-DMT)

Hallucinogenic drug found in certain South American plants. Its street name is “foxy” or “foxy methoxy.” [15]

3-methoxy-4-hydroxy-phenylglycol (MHPG)

A metabolite of NE, formed primarily as a result of NE breakdown in the brain. [5]

3,4-methylenedioxymethamphetamine (MDMA)

Drug similar in structure to amphetamine that stimulates 5-HT release and is neurotoxic at high doses. It is a recreational drug that is often abused. [6]

1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)

Dopamine neurotoxin sometimes used to produce an animal model of Parkinson’s disease. [5]

methyllycaconitine (MLA)

Blocks low-affinity nAChRs consisting only of α7 subunits. [13]

methylone

Cathinone derivative (3,4-methylenedioxy-N-methylcathinone) that is an abused stimulant drug. It is a member of a group of compounds sometimes called “bath salts,” “plant food,” “pond water cleaner,” and “legal highs.” [12]

methylphenidate (Ritalin)

Synthetic psychostimulant that is used to treat ADHD. [12]

methylxanthines

Class of naturally occurring chemicals that include caffeine and theophylline. [13]

metoprolol (Lopressor)

Drug that selectively blocks the β₁-receptor, limiting contraction of the heart muscles. It is useful for treating hypertension. [5]

Metrazol

See pentylenetetrazol. [8]

mGluR1–mGluR8

Eight metabotropic glutamate receptors of the nervous system. They can inhibit cyclic adenosine monophosphate synthesis, activate the phosphoinositide second-messenger system, or inhibit glutamate release into the synaptic cleft. [8]

MHPG

See 3-methoxy-4-hydroxy-phenylglycol. [5]

microdialysis

Technique used to measure neurotransmitter release in the brain of an awake, freely moving animal by collecting samples of extracellular fluid and then analyzing the samples biochemically using sensitive methods such as HPLC. Chemicals can also be applied to precise brain sites with the same technique. [4]

microelectrode

Device used to electrically stimulate or record the response of a single cell intracellularly or extracellularly. [4]

microglia

Small nonneuronal cells in the CNS that collect at points of cell damage or inflammation and demonstrate phagocytic behavior. [2]

microsomal enzymes

Enzymes in liver cells responsible for metabolizing exogenous substances such as drugs. [1]

microsomal ethanol oxidizing system (MEOS)

The cytochrome P450 enzyme CYP 2E1 that metabolizes ethanol and many other drugs. [10]

midsagittal

Section taken of the brain that divides it into left and right symmetrical pieces. [2]

mini-mental state exam (MMSE)

Cognitive test for measuring the severity of dementia. [20]

Minipress

See prazosin. [5]

mitochondria (sing. mitochrondrion)

Organelles of the cell that produce energy, in the form of ATP, from glucose. [2]

MK-801 (dizocilpine)

Drug that binds to the PCP site and acts as a noncompetitive antagonist of the NMDA receptor. [8]

moclobemide

Selective MAO-A inhibitor approved in several countries outside of the United States for the treatment of depression and social anxiety. [5]

modafinil (Provigil)

Synthetic psychostimulant that is used to treat patients with narcolepsy who exhibit excessive daytime sleepiness, people with obstructive sleep apnea, and people with disordered sleep due to shift work. [12]

monoacyl-glycerol lipase (MAGL)

Enzyme primarily responsible for metabolism of the endocannabinoid 2-arachidonoylglycerol. [14]

monoamine

Refers to a compound or transmitter that contains a single amine group. [3, 5]

monoamine hypothesis

Theory that a reduced level of monoamines in the CNS will cause depressed moods, including clinical depression. [18]

monoamine oxidase (MAO)

Enzyme responsible for metabolic breakdown of catecholamines and serotonin. [5]

monoamine oxidase inhibitors (MAOIs)

Class of drugs that inhibit monoamine oxidase (MAO), thereby causing an accumulation of catecholamines and serotonin in the brain. They are often used to treat clinical depression. [20]

moral model

Model of addiction that treats addiction as a personal and moral problem. [9]

Morris water maze

Maze type that involves repeatedly placing the animal in a pool of opaque water and testing its ability to use visual cues from outside the pool to find the escape platform. It is used to test spatial learning. [4]

motor efferents

Nerve fibers originating in the CNS and traveling to the skeletal muscles, controlling voluntary movements. [2]

motor neurons

Nerve cells that transmit electrical signals from the CNS to muscles. [2]

MPTP

See 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. [5, 20]

MRI

See magnetic resonance imaging. [4]

MS

See multiple sclerosis. [20]

multidimensional approach

Treatment that involves a combination of methods to prevent drug abuse relapse, including detoxification, pharmacological support, and counseling. [11]

multiple sclerosis (MS)

Disorder caused by autoimmune destruction of the myelin covering neurons in the brain and spinal cord. MS affects movement, sensation, and bodily functions. [20]

multiple T-maze

Maze type that contains many alleys ending in a “T” shape, which gives the animal two possible directions at each choice point. [4]

μ-receptor

A subtype of opioid receptor located in the brain and spinal cord that has a high affinity for morphine and certain other opiate drugs. [11]

muscarinic receptors

Family of metabotropic cholinergic receptors that are selectively stimulated by muscarine. [7]

muscimol

Drug found in the mushroom Amanita muscaria that is an agonist for the GABA_A receptor. [8]

muscle dysmorphia

Psychological disorder characterized by a false perception that the sufferer is weak and small, constant checking of one’s appearance, concealing one’s body shape, and a preoccupation with working out and using steroids to enhance muscle growth. [16]

muscle relaxants

Drugs, such as benzodiazepines, that reduce muscle tension in a patient. [17]

mutant mice

Genetically modified mice produced by gene disruptions: knockout, knockin, or transgenic manipulations. They are used to study genetic disorders. [18]

myasthenia gravis

Neuromuscular disorder involving an attack on the muscle cholinergic receptors by one’s own immune system. [7]

myelin

A fatty insulating sheath surrounding many axons that increases the speed of nerve conduction. It is produced by oligodendrocytes in the CNS and by Schwann cells in the peripheral nervous system. [2]

N

N-benzylphenethylamines (NBOMes)

Relatively new class of potent synthetic hallucinogens. [15]

N-methyl-<span="smallcap">d-aspartate (NMDA)

An exogenous amino acid derivative that has high affinity for a specific subtype of ionotropic glutamate receptors. [20]

Na⁺–K⁺ pump

An enzyme (Na⁺-K⁺ ATPase) that helps to maintain the resting membrane potential by removing Na⁺ from inside the cell. Three Na⁺ ions are exchanged for two K⁺ ions, maintaining a negative charge inside the cell. It also forces the ions against their concentration gradients following an action potential. [2]

NAcc

See nucleus accumbens. [2]

nAChRs

See nicotinic acetylcholine receptors. [13]

nalmefene

A dual κ/μ-opioid antagonist effective in reducing lever pressing for alcohol in rodent studies, particularly in alcohol-dependent animals. [10]

naltrexone

A μ-receptor antagonist that reduces consumption and craving in some alcoholic individuals, perhaps by reducing the positive feeling caused by alcohol. [10]

Namenda

See memantine. [8, 20]

narcolepsy

Sleep disorder characterized by repeated bouts of extreme sleepiness during the daytime. Symptoms include sudden cataplexy, sleep paralysis, and dream-like hallucinations. [3]

narcotic analgesics

Class of drugs originally derived from the opium poppy that reduce pain but do not cause unconsciousness. They create a feeling of relaxation and sleep in an individual, but in high doses can cause coma or death. [11]

Nardil

See phenelzine. [5]

natural recovery

Recovery from drug addiction without the aid of treatment. [9]

NBOMes

See N-benzylphenethylamines. [15]

NBQX

Antagonist that blocks both AMPA and kainate receptors, but has no effect on NMDA receptors. [8]

NE transporter

Protein in the membrane of noradrenergic neurons that is responsible for NE reuptake from the synaptic cleft. [5]

NE

See norepinephrine. [3, 5]

necroptosis

See programmed necrosis. [8]

necrosis

Cell death resulting from exposure to a chemical agent (such as glutamate), disease, or other injury. It differs in several important ways from apoptosis (programmed cell death). [8]

negative symptoms

Characteristics of schizophrenia that are observed as a decline in normal function, such as reduced speech, loss of motivation, social withdrawal, and anhedonia. [19]

neonatal ventral hippocampal lesion model (NVHL)

Neurodevelopmental model of schizophrenia that relies on early damage to the hippocampus in rodents. Hippocampal lesioning leads to some behaviors analogous to the early negative symptoms of schizophrenia. Behaviors similar to the positive symptoms of psychosis appear only at post-adolescence. [19]

neostigmine (Prostigmin)

Synthetic analog of the drug physostigmine that cannot cross the blood–brain barrier. It is used to treat myasthenia gravis due to its ability to block AChE activity in muscle tissue. [7]

nerves

Bundles of neurons outside the CNS that transmit electrical signals for nervous system function. [2]

neuraxis

Imposed line through the body that starts at the base of the spinal cord and ends at the front of the brain. [2]

neuroadaptations

Changes in brain functioning that attempt to compensate for the effects of repeated substance use. [9]

neurodevelopmental model

Theory that genetic vulnerability in combination with environmental stressors alters the trajectory of brain development resulting in the symptoms observed in schizophrenics. [19]

neurofibrillary tangles (NFTs)

Fibrous inclusions, composed primarily of tau protein, that are abnormally located in the cytoplasm of neurons. Pyramidal neurons are particularly susceptible to NFTs. [20]

neuroleptic malignant syndrome (NMS)

Undesired response to antipsychotic drugs characterized by fever, instability of the autonomic nervous system, rigidity, and altered consciousness. [19]

neuroleptics

Drugs useful in treating schizophrenia; an older term that refers to their ability to selectively reduce emotionality and psychomotor activity. Now more often called antipsychotics.[19]

neuromodulators

Chemicals that don’t follow the typical neurotransmitter model. They may regulate neurotransmitter activity or act at distant sites from their point of release. [3]

neuromuscular junction

Connection point between neurons and muscle cells. It has some of the characteristics of a synapse. [3, 7]

neurons

Nerve cells that form the brain, spinal cord, and nerves and that transmit electrical signals throughout the body. [2]

neuropathic pain

Chronic pain caused by nerve tissue damage. Produced within the nervous system itself, not in response to a nociceptive stimulus like a stab wound or burn. [6, 14]

neuropeptides

Small proteins (3 to 40 amino acids long) in the nervous system that act as neurotransmitters. [3]

neuropharmacology

Area of pharmacology specializing in drug-induced changes to the function of cells in the nervous system. [1]

neuropsychopharmacology

Area of pharmacology focusing on chemical substances that interact with the nervous system to alter behavior, emotions, and cognition. [1]

neurosteroids

Family of substances that are synthesized in the brain from cholesterol and that have a steroid structure. They act as local signaling agents. [8]

neurotoxin

Chemical that damages or kills nerve cells without damaging axons in the area. [4, 5]

neurotransmitters

Chemical substance packaged in synaptic vesicles and released by a neuron to communicate across a synapse with another neuron, muscle cell, organ, or a hormone-producing cell in an endocrine gland. [2, 3]

neurotrophic factors

Proteins that encourage the growth, development, and survival of neurons. They are also involved in neuronal signaling. [3]

neurotrophic hypothesis

Theory that low BDNF is responsible for the loss of dendritic branches and spines and reduced volume of brain areas responsible for clinical depression. [18]

NFTs

See neurofibrillary tangles. [20]

nicotine replacement therapy (NRT)

Method to stop smoking that involves giving the smoker a safer nicotine source, thereby maintaining a level of nicotine in the body and reducing nicotine withdrawal symptoms. [13]

nicotine resource model

Theory that smoking is maintained due to positive effects of nicotine such as increased concentration and greater mood control. [13]

nicotinic acetylcholine receptors (nAChRs)

Family of ionotropic receptors that are activated by ACh and selectively stimulated by nicotine. They may also be called nicotinic receptors. [13]

nicotinic cholinergic receptors (nAChRs)

See nicotinic receptors. [7]

nicotinic receptors

Family of ionotropic receptors that are activated by ACh and selectively stimulated by nicotine. They may also be called nicotinic cholinergic receptors. [7]

nigrostriatal tract

Dopaminergic nerve tract originating at the substantia nigra and terminating in the stratum. It is important for regulation of movement and is severely damaged in Parkinson’s disease. [5]

nitrites

Class of inhalants that are characterized by the presence of an NO₂ group and that heighten sexual arousal and pleasure. [16]

nitrosamines

Class of toxic chemicals contained in tobacco cigarette smoke that have been implicated in smoking-related carcinogenesis and other disease mechanisms. [13]

NMDA receptor

Ionotropic glutamate receptor selective for the agonist NMDA. [8]

NMS

See neuroleptic malignant syndrome. [19]

nocebo

Substance that is pharmacologically inert, yet can produce negative therapeutic outcomes. [1]

nodes of Ranvier

Gaps in the myelin sheath that expose the axon to the extracellular fluid. [2]

noncompetitive antagonists

Drugs that reduce the effect of an agonist, but do not compete at the receptor site. The drug may bind to an inactive portion of the receptor, disturb the cell membrane around the receptor, or interrupt the intercellular processes initiated by the agonist–receptor association. [1]

nonspecific drug effects

Physical or behavioral changes not associated with the chemical activity of the drug–receptor interaction but with certain unique characteristics of the individual such as present mood or expectations of drug effects. [1]

nonsteroidal anti-inflammatory drugs (NSAIDs)

COX-2 inhibitors such as ibuprofen. [14]

nootropics

Drugs that enhance cognitive function, especially memory. [8]

NOP-R

One of the four opioid receptors. It is widely distributed in the CNS and the peripheral nervous system and is activated by the neuropeptide nociceptin/orphanin FQ. [11]

noradrenergic

Adjectival form of noradrenaline (norepinephrine). [5]

norepinephrine (NE)

Neurotransmitter related to DA that belongs to a group called catecholamines. It also functions as a hormone secreted by the chromaffin cells of the adrenal medulla. Also known as noradrenaline. [3, 5]

Norflex

See orphenadrine. [7]

novelty suppressed feeding paradigm

An experimental technique to evaluate anxiety that measures the latency to eat novel foods in a familiar environment or usual foods in a novel environment. [4]

NRT

See nicotine replacement therapy. [13]

NSAIDs

See nonsteroidal anti-inflammatory drugs. [14]

nuclei

Localized cluster of nerve cell bodies in the brain or spinal cord. [2]

nucleus accumbens (NAcc)

Structure of the limbic system that mediates the reinforcing and incentive salience effects of many activities, including the abuse of drugs. [2]

Nuedexta

Dextromethorphan-containing medication prescribed for the treatment of pseudobulbar affect. [15]

NVHL

See neonatal ventral hippocampal lesion model. [19]

O

obsessions

Worrying thoughts or ideas that an individual cannot easily ignore. [17]

obsessive-compulsive disorder (OCD)

Psychiatric anxiety disorder characterized by persistent thoughts of contamination, violence, sex, or religion that the individual cannot easily ignore, and that cause the individual anxiety, guilt, or shame, etc. and may be accompanied by compulsive repetitive behaviors. [17]

occipital lobe

One of four lobes of the cerebral cortex. It contains the visual cortex and helps integrate visual information. [2]

OCD

See obsessive-compulsive disorder. [17]

6-OHDA

See 6-hydroxydopamine. [5]

8-OH-DPAT

See 8-hydroxy-2-(di-n-propylamino) tetralin. [6]

oligoclonal bands

Immunoglobins that indicate inflammatory processes within the central nervous system. [20]

oligodendrocytes

Glial cells that myelinate nerve axons of the CNS. Also known as oligodendroglia. [20]

oligodendroglia

Glial cells that myelinate nerve axons of the CNS. Also known as oligodendrocytes. [2]

ondansetron (Zofran)

Drug that inhibits 5-HT₃ receptors. It is used to treat the nausea and vomiting side effects of cancer chemotherapy. [6]

one-chamber social interaction test

Test used to measure the level of anxiety in rodents by recording the time spent investigating other animals. [4]

open

State of a receptor channel in which the channel pore is open, thereby permitting ion flow across the cell membrane. [7]

open field test

Technique used to measure locomotor activity and exploratory behavior by placing the animal on a grid and recording the number of squares traversed in a unit of time. [4]

operant analgesia testing

Technique used to test analgesic drugs. Once an animal is trained to lever press to terminate foot shock, the researchers gradually increase shock stimulation from very low levels until the animal responds by lever pressing, to indicate threshold. Analgesic drugs would be expected to raise that threshold. [4]

operant conditioning

Type of learning in which animals learn to respond to obtain rewards and avoid punishment. It explains drug tolerance when an animal learns to engage in behaviors when under the influence of a drug. [1]

opponent-process model

Model of addiction in which the initial positive response to a drug is followed by an opposing withdrawal response as the drug wears off. [9]

optogenetics

New neurobiological technique based on the ability of certain light-sensitive proteins, when expressed in a specific subset of neurons, to either excite or inhibit the cells when exposed to light of the appropriate wavelength. [4]

oral administration (PO)

Method that involves administering a drug through the mouth. [1]

orexin-A

Peptide neurotransmitter, also known as hypocretin 1, which is found in the hypothalamic area and which regulates numerous behavioral and physiological functions including feeding behavior, body weight, reward, emotional responses, stress responses, and autonomic nervous system activity. [3]

orexin-B

Peptide neurotransmitter, also known as hypocretin 2, which is found in the hypothalamic area and which regulates numerous behavioral and physiological functions including feeding behavior, body weight, reward, emotional responses, stress responses, and autonomic nervous system activity. [3]

organophosphorus compounds

General name for organic chemicals containing phosphorus, but sometimes applied more specifically to esters of phosphoric acid. OPs are the basis for many insecticides, herbicides, and nerve gases. [7]

orphenadrine (Norflex)

Anticholinergic drug used to treat early symptoms of Parkinson’s disease. [7]

osmotic minipump

Device placed just under the skin of an animal that allows a drug to be administered continuously over a set period of time. [13]

other hallucinogen use disorder

DSM-5 diagnostic category that defines a psychiatric disorder involving use of hallucinogenic drugs other than PCP and related substances. [15]

ovaries

Female-specific gonads that secrete the sex hormones estrogen and progesterone. [3]

oxytocin

Peptide hormone synthesized by certain hypothalamic neurons and secreted into the bloodstream at the posterior lobe of the pituitary gland. Circulating oxytocin induces uterine contractions during childbirth and milk letdown during lactation. Other oxytocin neurons form synapses within the brain and play an important role in social, including maternal, behaviors in some species. [3]

P

P2X receptors

Ionotropic receptors for ATP. [13]

P2Y receptors

Metabotropic receptors for ATP. [13]

PAG

See periaqueductal gray. [2]

palonosetron (Aloxi)

Drug that inhibits 5-HT₃ receptors. It is used to treat the nausea and vomiting side effects of cancer chemotherapy. [6]

panic attack

Feeling of extreme fear that was not preceded by a threatening stimulus. [17]

panic disorder

Disease involving repeated attacks of extreme fear, occurring either without warning or in an environment similar to where previous panic attacks occurred. [17]

pannexins

Membrane channels through which ATP is released into the extracellular fluid. [13]

para-chloroamphetamine

Drug similar in structure to amphetamine that stimulates 5-HT release. It is also neurotoxic at high doses. [6]

para-chlorophenylalanine (PCPA)

Drug that irreversibly inhibits tryptophan hydroxylase, blocking 5-HT synthesis. [6]

parasympathetic

Division of the autonomic nervous system responsible for conserving energy, digestion, glucose and nutrient storage, slowing the heart rate, and decreasing respiration. [2]

parasympatholytic agents

Drugs that block muscarinic receptors, inhibiting the parasympathetic system. They are deadly at high doses, but at low doses they are used medicinally to dilate pupils, relax airways, counteract cholinergic agonists, and induce drowsiness. [7]

parasympathomimetic agents

Drugs that stimulate muscarinic receptors, thereby mimicking the effects of parasympathetic system activation. [7]

parenteral

Methods of drug administration that do not use the gastrointestinal system, such as intravenous, inhalation, intramuscular, transdermal, etc. [1]

parietal lobe

One of four lobes of the cerebral cortex. It contains the somatosensory cortex and helps integrate information about body senses. [2]

Parkinson’s disease (PD)

Chronic, progressive, neurodegenerative disorder characterized by tremor, rigidity, difficulty in initiating movement, slowing of movement, and postural instability. [20]

Parkinson’s disease dementia (PDD)

Condition in which one or more cognitive functions are impaired to the point of interfering with the ability of the individual to navigate everyday life. [20]

Parkinsonian symptoms

Undesired response to anti-psychotic drugs that resembles Parkinson’s disease, including tremors, akinesia, muscle rigidity, akathesia, and lack of facial expression. [19]

Parnate

See tranylcypromine. [5]

paroxysmal depolarization shift (PDS)

Periodic episodes of prolonged neuronal depolarization occurring during the interictal period in the brain of epileptic patients. [8]

partial agonists

Drugs that bind to a receptor but have low efficacy, producing weaker biological effects than a full agonist. Hence, they act as agonists at some receptors and antagonists at others, depending on the regional concentration of full agonist. These were previously called mixed agonist-antagonists. [1, 11]

parts per million (ppm)

Number of molecules of a gaseous substance per million molecules of air. When applied to an inhaled substance, it is used to describe the amount of exposure to the substance (i.e., dose). [16]

passive avoidance learning

Type of learning task in rats and mice in which the animal is trained to avoid a location that it would normally enter (e.g., going into a dark compartment from one that is brightly lit) by administeration of a brief electric footshock when it enters the location. The word “passive” in the name of the task reflects the fact that the animal must withhold its usual response of moving into the dark compartment. [5]

passive diffusion

Movement of lipid-soluble materials across a biological barrier without assistance based on its concentration gradient, from higher to lower concentration. [1]

patch clamp electrophysiology

Technique used to measure the function of a single ion channel by using a micropipette to isolate the ion channel and obtain an electrical recording. [4]

Pavlovian conditioning

See classical conditioning. [1]

PCP

See phencyclidine. [8, 15]

PCPA

See para-chlorophenylalanine. [6]

PDE

See phosphodiesterase. [18]

PDS

See paroxysmal depoarization shift. [8]

peak experience

Intense psychedelic state experienced during a hallucinogenic drug-assisted therapeutic session that is hypothesized to be an important contributor to the therapeutic benefit. [15]

pedunculopontine tegmental nuclei (PPTg)

Structure within the dorsal lateral pons containing cholinergic neurons that project to the substantia nigra (important for stimulating nigral dopamine neurons) and others that project to the brainstem and thalamus (important for behavioral arousal, sensory processing, and inititation of rapid-eye-movement sleep). [7]

penetrance

Frequency with which a particular gene produces its main effect. [20]

pentylenetetrazol (Metrazol)

Convulsant drug that acts by blocking the function of GABA_A receptors. [8]

penumbra

Following an ischemic stroke, this is the outer region of damage (surrounding the core) within which the dying neurons can potentially be rescued. [8]

periaqueductal gray (PAG)

Structure of the tegmentum located around the cerebral aqueduct that connects the third and fourth ventricles. It is important for regulating pain; stimulation produces an analgesic effect. [2]

PET

See positron emission tomography. [4]

peyote button

Crown of the peyote cactus, Lophophora williamsii, that can be dried and ingested to obtain the hallucinogenic drug mescaline. [15]

peyote cactus

Species of cactus, Lophophora williamsii, that produces mescaline. [15]

pharmacodynamic tolerance

Type of tolerance formed by changes in nerve cell functions in response to the continued presence of a drug. [1]

pharmacodynamic tolerance

Type of tolerance formed by changes in nerve cell functions in response to the continued presence of a drug. [10]

pharmacodynamics

Study of physiological and biochemical interactions of a drug with the target tissue responsible for the drug’s effects. [1]

pharmacogenetics

The study of the genetic basis for variability in drug response among individuals (sometimes called pharmacogenomics). [1]

pharmacokinetic

Factors that contribute to bioavailability: the administration, absorption, distribution, binding, inactivation, and excretion of a drug. [1]

pharmacological MRI (phMRI)

A spin-off of functional MRI (fMRI), is a technique used in drug development to investigate the mechanism of drug action by visualizing changes in brain function following drug administration. [4]

pharmacology

Study of the actions of drugs and their effects on living organisms. [1]

pharmacotherapeutic treatment

Method of disease treatment that uses drugs to modify a clinical condition. [10]

phasic release

Irregularly timed and larger amounts of neurotransmitter release than occurs in the case of tonic release. It is typically associated with burst mode of cell firing and produces surges in extracellular levels of the transmitter. [5]

phencyclidine (PCP)

Drug that binds to the PCP site and acts as a noncompetitive antagonist of the NMDA receptor. It is a dissociative anesthetic that was once used medicinally but is now only taken recreationally. [8, 15]

phenelzine (Nardil)

MAO inhibitor used to treat clinical depression. [5]

phenethylamine

Class of drugs that includes mescaline as well as NE- and amphetamine-related substances. [15]

phenylephrine

α₁-receptor agonist that causes behavioral stimulation. [5]

phMRI

See pharmacological MRI. [4]

phobias

Fears of specific objects or situations that are recognized as irrational. [17]

phosphodiesterase (PDE)

The enzyme that normally degrades cAMP to 5′-AMP. [18]

phosphoinositide second-messenger system

Neurotransmitter signaling mechanism that activates PKC and is controlled by certain receptors for ACh, NE, and 5-HT. [3]

phospholipids

Lipid molecules that are major constituents of the cell membrane. They are composed of a polar head and two lipid tails. [1]

phosphorylate

Add a phosphate group to a molecule by means of an enzymatic reaction. [3]

physical dependence

Developed need for a drug, such as alcohol or opioids, by the body as a result of prolonged drug use. Termination of drug use will lead to withdrawal symptoms (abstinence). [1, 10, 11]

physiological antagonism

Drug interaction characterized by two drugs that act in distinct ways and reduce each other’s effectiveness in the body. [1]

physostigmine (eserine)

Drug that blocks AChE activity. Its symptoms include slurred speech, mental confusion, hallucinations, loss of reflexes, convulsions, coma, and death. It is isolated from Calabar beans [7]

phytocannabinoids

Compounds with a cannabinoid structure that are found in the cannabis plant. [14]

pia mater

The innermost of the meninges. The pia mater is a thin tissue immediately surrounding the brain and spinal cord. [2]

picrotoxin

Convulsant drug that acts by blocking the function of GABA_A receptors. [8]

pilocarpine

Extract of the shrub Pilocarpus jaborandi known for its ability to stimulate muscarinic receptors. [7]

pineal gland

Specific endocrine gland that is located above the brain stem, covered by the cerebral hemispheres. It secretes melatonin. [3]

pinocytotic vesicles

Type of vesicles that envelop and transport large molecules across the capillary wall. [1]

pituitary gland

Endocrine gland that is located under the hypothalamus and connects to the brain by a thin stalk. It secretes TSH, ACTH, FSH, LH, GH, PRL, vasopressin, and oxytocin. [3]

PKA

See protein kinase A. [3]

PKC

See protein kinase C. [3]

PKG

See protein kinase G. [3]

place conditioning

Pavlovian conditioning procedure used to test the rewarding effects of drugs in rats and mice. [9]

placebo

Substance that is pharmacologically inert, yet in many instances produces both therapeutic and side effects. [1]

PO

See oral administration. [1]

polarized

Possessing an electrical charge. [2]

polypharmacy

Use of multiple pharmacological agents at the same time. [16]

POMC

See pro-opiomelanocortin. [11]

positive reinforcers

Something (e.g., an abused drug) that, when provided to an organism, increases the strength of the response that was used to obtain the item. In studies of addiction, the positive reinforcing quality of a drug is usually measured by means of a self-administration procedure. [9]

positive symptoms

Characteristics of schizophrenia that include delusions, hallucinations, disorganized speech, and bizarre behavior. They are often the more dramatic symptoms. [19]

positron emission tomography (PET)

Imaging technique used to determine the distribution of a radioactively labeled substance in the body. It can be used to measure drug binding to neurotransmitter receptors or transporters in the brain as well as measuring changes in metabolic activity reflecting neuron function. [4]

post-traumatic stress disorder (PTSD)

Emotional disorder that develops in response to a traumatic event, leaving the individual feeling a sense of fear, helplessness, and terror. Symptoms include sleep disturbances, avoidance of stimuli associated with the trauma, intrusive thoughts reliving the event, and a numbing of general emotional responses. An increase in suicidal thoughts has also been observed. [17]

posterior

Located near the back or rear of the nervous system. [2]

posterior pituitary

Part of the pituitary gland in which vasopressin and oxytocin are secreted. [3]

postsynaptic cell

Neuron at a synapse that receives a signal from the presynaptic cell. [3]

postsynaptic density

Protein-rich structure associated with the postsynaptic membrane of many dendrites that contains a high density of neurotransmitter receptors along with other proteins that anchor the receptors to the postsynaptic area near the presynaptic sites of transmitter release. [3]

postural instability

Impaired balance and coordination. In Parkinson’s disease, manifests as a pronounced forward or backward lean in upright position. [20]

potency

Measure of the amount of drug necessary to produce a specific response. It is dependent on the affinity of the drug to the receptor. [1]

potentiation

Drug interaction characterized by an increase in effectiveness greater than the collective sum of the individual drugs. [1]

PPI

See prepulse inhibition of startle. [4, 19]

PPTg

See pedunculopontine tegmental nucleus. [7]

prazosin (Minipress)

α₁-receptor antagonist that causes dilation of blood vessels and is useful for treating hypertension. [5]

Precedex

See dexmedetomidine. [5]

precipitated withdrawal

Method used to test dependence and withdrawal by administering an antagonist to block drug effects rapidly. [14]

precursor

Chemical that is used to make the product formed in a biochemical pathway (e.g., tyrosine is the precursor of DOPA in the pathway for catecholamine synthesis). [3]

predictive validity

A measure of how closely the results from animal tests predict clinically useful effects in humans. [4]

prenatal inflammation

After administration of pro-inflammatory agents to pregnant rodents, neurodevelopmental and behavioral outcomes are evaluated in the offspring. [19]

prepulse inhibition of startle (PPI)

Method to study the ability of an individual to filter out sensory stimuli by applying a weak “prepulse” stimulus shortly before the startle-inducing stimulus. Well validated model of information-processing deficits in schizophrenia. [4, 19]

presenilin-1 (PS-1)

Protein involved in the processing of APP. [20]

presenilin-2 (PS-2)

Protein involved in the processing of APP. [20]

presurgical anesthesics

Drugs used to decrease preoperative anxiety to make administration of the surgical anesthesia less distressing and quicker. [17]

presynaptic cell

Neuron at a synapse that transmits a signal to the postsynaptic cell. [3]

presynaptic facilitation

Signaling by the presynaptic cell to increase neurotransmitter release by the axon terminal of the postsynaptic cell. [3]

presynaptic inhibition

Signaling by the presynaptic cell to reduce neurotransmitter release by the axon terminal of the postsynaptic cell. [3]

primary cortex

The part of each lobe of the cortex that provides conscious awareness of sensory experience and the initial cortical processing of sensory qualities. [2]

primary hypogonadism

Type of hypogonadism caused by lack of responsiveness of the testes to LH and FSH. [16]

PRL

See prolactin. [3]

pro-opiomelanocortin (POMC)

One of the four large opioid propeptide precursors that are broken down by proteases to form smaller active opioids (endorphins) in the brain. [11]

prodynorphin

One of the four large opioid propeptide precursors that are broken down by proteases to form smaller active opioids (dynorphins) in the brain. [11]

proenkephalin

One of the four large opioid propeptide precursors that are broken down by proteases to form smaller active opioids (enkephalins) in the brain. [11]

progesterone

Female sex hormone secreted by the ovaries that is present at high levels during pregnancy. [3]

progestins

Group of female sex hormones that are important for the maintenance of pregnancy. The principal naturally occurring progestin is progesterone. [3]

programmed cell death

Cell death resulting from a programmed series of biochemical events in the cell designed to eliminate unnecessary cells. Also called apoptosis. [8]

programmed necrosis

Type of programmed cell death provoked by excitotoxic treatment of adult animals in which the appearance of the dying neurons is different from the appearance of neurons undergoing apoptosis. Also called necroptosis. [8]

progressive-ratio procedure

Method used to measure the relative power of drug reinforcement by steadily increasing the response to reward ratio. [9]

prolactin (PRL)

Hormone secreted by the anterior pituitary that promotes milk production by the mammary glands. [3]

promoter region

Section of a gene, adjacent to the coding region, that controls the rate of transcription as directed by the binding of transcription factors. [2]

pronociceptin/orphanin FQ

One of the four large opioid propeptide precursors, that is broken down by proteases to form smaller active opioids (nociceptin, orphanin FQ) in the brain. [11]

propofol (Diprivan)

Positive allosteric modulator of the GABA_A receptor that is used as a surgical anaesthetic agent. [8]

propranolol (Inderal)

β-receptor antagonist. It is useful for treating hypertension due to its ability to block β-receptors in the heart, thereby limiting contraction of the heart muscles. [5]

Prostigmin

See neostigmine. [7]

protein kinase A (PKA)

Enzyme that is stimulated by cAMP and that phosphorylates specific proteins as part of a neurotransmitter signaling pathway. [3]

protein kinase C (PKC)

Enzyme that is stimulated by diacylglycerol and Ca²⁺ and that phosphorylates specific proteins as part of a neurotransmitter signaling pathway. [3]

protein kinase G (PKG)

Enzyme that is stimulated by cGMP and that phosphorylates specific proteins, including proteins involved in cell growth and differentiation. [3]

protein kinases

Enzymes that catalyze the phosphorylation of other proteins. [3]

Provigil

See modafinil. [12]

Prozac

See fluoxetine. [6]

prucalopride (Resolor)

Drug that stimulates 5-HT₄ receptors. It is used to treat the diarrhea-predominant form of irritable bowel syndrome in several countries outside of the United States. [6]

pseudobulbar affect

Rare neurological disorder seen in a small percentage of patients with brain injury or disease that is characterized by frequent, uncontrollable episodes of laughing or crying that are incongruent with the person’s emotional state. [15]

psilocin

Metabolite of psilocybin. Psilocin is the actual psychoactive agent. [15]

psilocybin

Hallucinogenic drug found in several mushroom species. [15]

psychedelic

Substance that alters perceptions, state of mind or awareness. [15]

psychedelic therapy

Therapeutic method that involved giving patients a single high dose of LSD to help them understand their problems by reaching a drug-induced spiritual state. [15]

psychoactive drugs

Those drugs that have an effect on thinking, mood, or behavior. [1]

psycholytic therapy

Therapeutic method that employed LSD in low doses, gradually increasing the dose, in attempts to recover repressed memories or increase communication with the therapist. [15]

psychomotor stimulants

Class of drugs that produce strong sensorimotor activation characterized by increased alertness, heightened arousal, and behavioral excitation. Also called psychostimulants. [12]

psychopharmacology

Area of pharmacology specializing in drug-induced changes in mood, thinking, and behavior. [1]

psychosocial rehabilitation

Counseling programs that involve educating the user, promoting behavioral change and alleviating problems caused by drug use. [10]

psychosocial treatment programs

Counseling programs that involve educating the user, promoting behavioral change and alleviating problems caused by drug use. [12]

psychotomimetic

Substance that mimics psychosis in a subject, such as by inducing hallucinations or delusions. [15]

PTSD

See post-traumatic stress disorder. [17]

pure antagonists

Drug that produces no pharmacological activity (i.e., no efficacy) and that can prevent or reverse the effects of a drug agonist by occupying the receptor site. [11]

pyramidal neuron

Neuron with a roughly pyramidal shape that serves as the principal type of output neuron in several brain areas, notably the cerebral cortex, hippocampus, and amygdala. [3]

pyramiding

Pattern of steroid use characterized by gradually increasing the drug dose until the middle of the cycle, then gradually decreasing the drug dose until the cycle is complete. [16]

pyridostigmine (Mestinon)

Synthetic analog of the drug physostigmine that cannot cross the blood–brain barrier. It is used to treat myasthenia gravis due to its ability to block AChE activity in muscle tissue. [7]

pyrolysis

Process of chemical decomposition caused by heating. [13]

Q

quantitative EEG (qEEG)

Computer-assisted evaluation of EEG data, used to monitor brain function and cognitive processing. [4]

quinpirole

Agonist at D₂ and D₃ dopamine receptors. [5]

R

radial arm maze

Maze type composed of multiple arms leading from a central choice point. Radial arm mazes are used to test spatial learning. [4]

radioimmunoassay (RIA)

A very sensitive method that uses antibodies to measure molecules in body fluids or tissue extracts. The essay depends on competitive binding of an antibody to the antigen of interest. [4]

radioligand binding

Technique used to measure the affinity and relative density of receptors in a particular brain area by using a radioactively labeled ligand for the receptor. [4]

raphe nuclei

Network of cell clusters in the CNS that contain the cell bodies of serotonergic neurons. They are found almost exclusively along the midline of the brain stem. [6]

rasagiline (Azilect)

Selective MAO-B inhibitor used clinically to elevate brain DA levels in Parkinson’s disease. [5]

rate-limiting enzyme

Enzyme that catalyzes the slowest step in a biochemical pathway. It determines the overall rate of product formation. [5]

reactive depression

State of sadness that is appropriate and of a reasonable level in response to a given aversive situation. Not usually considered a clinical condition. [18]

reboxetine (Edronax)

Antidepressant that selectively blocks the NE transporter, thereby increasing NE concentration in the synaptic cleft. [5]

receptor agonists

Neurochemicals or drugs that can bind to a particular receptor protein and alter the shape of the receptor to initiate a cellular response. [1]

receptor antagonists

Molecules that interact with a receptor protein and produce no cellular effect after binding, and also prevent an “active” ligand from binding. [1]

receptor binding studies

Technique used to measure the affinity and relative density of receptors in a particular brain area by using a radioactively labeled ligand for the receptor. Also called radioligand binding. [18]

receptor cloning

Process used to produce large amounts of identical receptor proteins in a cell line. [11]

receptor subtypes

Group of receptors that respond to the same neurotransmitter but that differ from each other to varying degrees with respect to their structure, signaling mechanisms, and pharmacology. [1, 3]

receptor trafficking

Normal process in which the receptors for a particular neurotransmitter are shuttled into and out of the cell membrane to regulate sensitivity of the cell to that transmitter. [8]

receptor up-regulation

Increase in the number of receptors produced and maintained in a target cell. [5]

receptors

Proteins located on the surface of or within cells that bind to specific ligands to initiate biological changes within the cell. [1, 2, 3]

rectal administration

Drug delivery method requiring placement of a drug-filled suppository into the rectum. [1]

reinstatement of drug-seeking behavior

Restoration of a behavior (e.g., an operant response) previously used to obtain a drug after that behavior had been extinguished. It is an animal model for relapse to drug use after a period of abstinence in chronic drug users. [9]

relapse prevention therapy

Treatment program for drug abusers that teaches an individual how to avoid and cope with high-risk situations. [12]

relapses

Recurrences of drug use following a period of abstinence. [9]

relative refractory period

Short hyperpolarizing phase after an action potential during which a more intense excitatory stimulus is necessary to obtain an action potential. [2]

reliability

Term used to indicate how dependable test results are and how likely the same test results will be found in subsequent trials. [4]

remissions

Periods in which an addict is drug free. [9]

resensitization

Receptor state characterized by the return of receptor function and a normal response to agonist stimulation. [7]

reserpine

Drug extracted from Rauwolfia serpentina (snake root) roots. It inhibits vesicular monoamine uptake by VMAT, thereby reducing monoamine levels in the central and peripheral nervous system. [5]

resident–intruder test

Test of aggressive behavior involving attack by a resident adult male rat or mouse against a strange intruder male. [6]

resting membrane potential

The difference in the electrical charge inside a neuron at rest compared to the outside. The inside of the cell is more negative, and that potential is –70 mV. [2]

resting tremor

Tremor that is present when the limb is relaxed. Can be present in the hand, foot, jaw or face. Generally disappears with intentional movement. [20]

resting-state fMRI (rs-fMRI)

This technique is a variation of fMRI that visualizes brain activity and connectivity in individuals when they are not actively engaged in a task that requires attention or task performance. [4]

reticular formation

Collection of nuclei within the core of the pons forming a network that extends into the midbrain and medulla. These nuclei are important for arousal, attention, sleep, muscle tone, and some cardiac and respiratory reflexes. [2]

retrograde messengers

Chemicals synthesized and released by a postsynaptic cell that diffuse into the nerve terminal of the presynaptic cell, often for the purpose of altering neurotransmitter release by the terminal. [3]

retrograde signaling

Signaling mechanism in which the endocannabinoid activates CB₁ receptors on nearby nerve terminals. [14]

retropulsion

The need to take a step backward when starting to walk. [20]

reuptake

Process that involves transport of neurotransmitters out of the synaptic cleft by the same cell that released them. [3]

reverse tolerance

Enhanced response to a particular drug after repeated drug exposure. Also called sensitization. [12]

reward circuit

Circuit of neurons that, when activated, mediates the rewarding effects of both natural rewards (e.g., food, water, sex) and drugs of abuse. [9]

RIA

See radioimmunoassay. [4]

ribosomes

Organelles in the cytoplasm that decode the nucleotide sequence provided by mRNA and link the appropriate amino acids together to form a protein. [2]

rigidity

Stiffness and inflexibility in the joints. Two types are present in Parkinson’s disease: “lead-pipe” rigidity, which is characterized by maintenance of inflexibility of the joint through the entire range of movement, and “cog-wheel” rigidity, which is characterized by a ratchet-like interruption in movement. [20]

riluzole

Drug that inhibits glutamate release and that is used to treat ALS. [8]

rimonabant

Antagonist selective for the CB1 receptor. It is also called SR 141716. [14]

risperidone (Risperdal)

Drug that inhibits 5-HT_2A and D₂ dopamine receptors. It is used to treat schizophrenia. [6]

Ritalin

See methylphenidate. [12]

ritanserin

Drug that inhibits 5-HT2A receptors. [6]

rivastigmine (Exelon)

Drug that blocks AChE activity. It is used in the treatment of Alzheimer’s disease. [7]

rostral

Located near the front or head end of the nervous system. [2]

rotarod

An animal test using a horizontally-oriented cylinder that is mechanically rotated at set speeds. Researchers time latency to fall (e.g., how long mice remain balanced on the rod). [4]

S

Sabril

See vigabatrin. [8]

saclofen

Chemical analog of baclofen that is a competitive antagonist at the GABA_B receptor. [8]

sagittal

Section that is taken parallel to the plane bisecting the nervous system into right and left halves. [2]

saltatory conduction

Mode of action potential conduction along a myelinated neuron characterized by jumps from one node of Ranvier to the next. [2]

salvinorin A

Active compound in the hallucinogenic plant Salvia divinorum; acts as a κ-opioid receptor agonist. [15]

sarin

Toxin that causes irreversible inhibition of AChE. It is used as a nerve agent for chemical warfare. [7]

SC

See subcutaneous. [1]

SCH 23390

D₁ receptor antagonist that may induce catalepsy when administered in high doses. [5]

Schedule of Controlled Substances

System established by the Controlled Substances Act in 1970 that classifies most substances with abuse potential into one of five schedules. Schedules I and II have the strictest guidelines. [9]

schedule of reinforcement

Predetermined schedule used to determine when an animal will be rewarded for performing a specific behavior. A fixed ratio (FR) schedule refers to rewards given after a set number of responses; a fixed interval (FI) schedule refers to rewards given to the first response that occurs after a set amount of time has elapsed. [4]

Schwann cells

Glial cells that myelinate peripheral nerve axons. [2, 20]

scopolamine

Drug that blocks muscarinic receptors. It is found in nightshade, Atropa belladonna, and in henbane, Hyoscyamus niger. [7]

second messenger

Substance that, when activated by signaling molecules bound to receptors in the cell membrane, will initiate biochemical processes within the cell. [3]

second-messenger systems

Biochemical pathways that use second messengers to mediate intercellular signaling. [3]

secondary cortex

Section of the cerebral cortex containing the neuronal circuits responsible for analyzing and recognizing information from the primary cortex, and for memory storage. [2]

secondary hypogonadism

Type of hypogonadism caused by a decline in LH and FSH secretion. [16]

section

Tissue slice showing structures of the body or nervous system. [2]

sedative–hypnotics

Class of drugs that depresses nervous system activity. They are used to produce relaxation, reduce anxiety, and induce sleep. [17]

selective D₂ receptor antagonists

Drugs that selectively block D₂ receptors, including sulpiride, raclopride, and remoxipride. [19]

selective serotonin reuptake inhibitors (SSRIs)

Anti-depressants used to treat major depression, panic and anxiety disorders, obsessive-compulsive disorder, obesity, and alcoholism by blocking the presynaptic membrane transporter for 5-HT. [6, 18, 20]

selegiline (Eldepryl)

Selective MAO-B inhibitor used clinically to elevate brain DA levels in Parkinson’s disease. [5]

self-administration method

Test used to measure the abuse potential of a drug by allowing an animal to give itself the drug doses. [4]

self-medication hypothesis

Theory that addiction is based on an effort by the individual to treat oneself for mood or other ill feelings. [9]

sensitization

Enhanced response to a particular drug after repeated drug exposure. Also called reverse tolerance. [1, 11, 12]

sensory afferents

Neurons carrying sensory information from the body surface or internal organs into the CNS. [2]

sensory neurons

Nerve cells that are sensitive to environmental stimuli and convert the physical stimuli into electrical signals that are sent to the CNS. [2]

serenics

Class of drugs capable of inducing a state of calmness, thereby reducing aggressive behaviors. [6]

serotonergic neurons

Neurons that use serotonin as their transmitter. [6]

serotonin

Neurotransmitter found in the central and peripheral nervous system and synthesized by serotonergic neurons. [6]

serotonin deficiency hypothesis of aggression

Hypothesis that low serotonergic activity in the CNS is associated with hyperaggressiveness. [6]

serotonin reuptake transporter (SERT)

Protein in the membrane that is responsible for serotonin (5-HT) reuptake from the synaptic cleft. [18]

serotonin syndrome

Effects associated with an overdose of SSRIs or serotonergic agonists, including severe agitation, disorientation, confusion, ataxia, muscle spasms, fever, shivering, chills, diarrhea, elevated blood pressure, and increased heart rate. [6, 18]

SERT

See 5-HT transporter and serotonin reuptake transporter. [6, 18]

shared etiology

Situation in which multiple disorders are caused by the same set of factors. [9]

side effects

Undesired physical or behavioral changes associated with a particular drug. [1]

silent receptors

See drug depots. [1]

single-nucleotide polymorphisms (SNPs)

Allelic variations in genes consisting of a changes in single nucleotides in one of the two copies of a gene. They are distinguished from mutations by having a prevalence of at least 1% in the population. [9]

single-photon emission computerized tomography (SPECT)

Imaging technique used to view changes in regional blood flow or drug binding by using radioactively labeled compounds injected or inhaled into the body. [4]

single-spiking mode

Mode of neuronal cell firing characterized by the production of single action potentials at intervals that may be regular or irregular, depending on the cell type. For midbrain DA neurons, the intervals are irregular. [5]

sinsemilla

The potent marijuana produced by preventing pollination and seed production in the female cannabis plants. [14]

SKF 38393

Selective dopamine D1 receptor agonist. [5]

sleep deprivation

Lack of proper sleep, either unintentional (e.g., jet lag), or intentional (such as all-night studying). [18]

sleep paralysis

Loss of muscle tone leading to a feeling of paralysis that occurs during the daytime in some patients with narcolepsy. [3]

SNPs

See single-nucleotide polymorphisms. [9]

sodium oxybate (Xyrem)

The sodium salt of γ-hydroxybutyrate (GHB). It is used as a treatment for narcolepsy. [16]

soma

Cell body of a neuron, containing all of the organelles needed to maintain the cell. [2]

soman

Toxin that causes irreversible inhibition of AChE. It is used as a nerve agent for chemical warfare. [7]

somatodendritic autoreceptors

Autoreceptors located on the dendrites or cell body that slow the rate of cell firing when activated. [3]

spasticity

Constant unwanted contraction of one or more muscle groups. [20]

specific drug effects

Physical or behavioral changes associated with biochemical interactions of a drug with the target site. [1]

specific neurotoxins

Chemical that damages a specific neural pathway leaving others intact. [4]

SPECT

See single-photon emission computerized tomography. [4]

spinal interneurons

Nerve cells with short axons within the spinal cord. [11]

SR 141716A

See rimonabant. [14]

SSRIs

See selective serotonin reuptake inhibitors. [6, 18, 20]

stacking

Pattern of anabolic steroid use characterized by the simultaneous use of multiple steroids, such as a short- and a long-acting steroid. [16]

state-dependent learning

Condition characterized by better performance of a particular task that was learned in a drugged state in the same drugged state, rather than in a nondrugged state. Tasks learned in a nondrugged state are likewise performed better in a nondrugged state. [1]

status epilepticus

Dangerous condition characterized either by continuous epileptic seizures or a sufficiently short period between seizures so that the patient has insufficient time to recover. [8]

steady state plasma level

The desired blood concentration of drug achieved when the absorption/distribution phase is equal to the metabolism/excretion phase. [1]

stereotyped behaviors

Repeated, relatively invariant behaviors associated with a particular situation or drug treatment. They often occur following a high dose of a psychostimulant such as cocaine or amphetamine. [5]

steroids

Class of hormones that are derived from cholesterol and regulate a variety of biochemical pathways. [3]

stop-signal task

Test used to evaluate impulsivity (e.g., lack of behavior control). It requires the subject (human or otherwise) to rapidly press one button or lever when a square is displayed, and the other button or lever when any other shape appears. Periodically, a tone, which is the “stop” signal, is sounded following the visual presentation. The tone indicates that the subject should withhold responding. [4]

Strattera

See atomoxetine. [5]

subcutaneous (SC)

Method that involves injection of a drug just below the skin. [1]

sublingual administration

Method of drug administration that requires placing the drug under the tongue in contact with the mucous membrane, which has a rich capillary network for rapid absorption into the blood. [1]

substance use disorders

New DSM-5 designations for psychiatric disorders with features typically associated with addiction. This designation replaces both substance abuse and substance dependence categories in DSM-IV. [9]

substance-induced disorders

New DSM-5 designations referring to reversible substance-specific syndromes caused by recent ingestion of a substance. [9]

substance-related disorders

New DSM-5 category that encompasses both substance use disorders and substance-induced disorders. [9]

substantia nigra

Collection of dopaminergic cell bodies within the tegmentum of the mesencephalon that innervate the striatum by way of the nigrostriatal tract. Damage to cells in this region leads to Parkinson’s disease. [2, 5, 20]

subunits

Individual protein components that must join in the cell membrane to form a complete receptor. [3, 7]

succinylcholine

Chemical similar to ACh that is resistant to metabolism by AChE. It is used as a muscle relaxant during some surgical procedures. [7]

sucrose preference test

A test dependent on rodents’ natural preference for sweet solutions. Failure to prefer a sucrose solution over water is an indication of anhedonia, a symptom of clinical depressive disorder in humans. [4]

sudden sniffing death syndrome

Fatal cardiac arrhythmia associated with inhalant use. [16]

sulci (sing. sulcus)

Small grooves of the cerebral cortex. [2]

sumatriptan (Imitrex)

Drug that stimulates 5-HT_1B/1D receptors, thereby causing constriction of cerebral blood vessels. It is used to treat migraine headaches. [6]

superior

Located near the top of the brain in humans. [2]

suppressor T cell

Type of T cell that reduces or suppresses the immune response of other T cells (or B cells) to an antigen. [20]

supraspinal

Located above the spinal cord or spine. [11]

suvorexant (Belsomra)

Antagonist at both OX1R and OX2R receptors that is approved for the treatment of chronic insomnia. [3]

suxamethonium

Drug that causes a short-term depolarization block of skeletal muscles. It is used as an adjunct to general anesthesia to produce muscular relaxation during surgery. [7]

swimming performance

A rodent test of coordination used in the study of motor deficit diseases. [4]

sympathetic

Division of the autonomic nervous system responsible for providing energy expenditure to deal with a challenge by triggering the “fight-or-flight” response: increasing heart rate, increasing blood pressure, stimulating adrenaline secretion, and increasing blood flow to skeletal muscles. [2]

sympathomimetic

Substance that produces symptoms of sympathetic nervous system activation. [12]

synapse

Structural unit of information transmission between two nerve cells. It consists of the presynaptic nerve terminal, the synaptic cleft, and a small area of the postsynaptic cell (typically associated with a dendrite or region of the cell body) that receives the incoming signal. [2, 3]

synaptic cleft

Small gap, about 20 nm wide, between the presynaptic and postsynaptic cells. [3]

synaptic plasticity

Ability of synapses to change structurally (i.e., growth of new synapses or loss of existing ones) and functionally (i.e., increased or decreased strength of existing synapses). In the adult nervous system, synaptic plasticity is particularly important for learning and memory and for the development of addiction following repeated exposure to abused drugs. [3]

synaptic vesicles

Sac-like structures located in the axon terminal that are filled with molecules of neurotransmitter. [2, 3]

synaptobrevin

Small protein located in synaptic vesicle membranes that plays a critical role in exocytotic fusion of vesicles with the axon terminal membrane. [3]

synesthesia

Mixing of sensations such that one kind of sensory stimulus creates a different kind of sensation, such as a color producing the sensation of sound. [15]

T

T cells

A type of white blood cell. [20]

T-maze

Maze type that involves an alley ending in a “T” shape, giving the animal two path choices to reach food in goal box. [4]

T3

See triiodothyronine. [3]

T4

See thyroxine. [3]

tail suspension test

Used in the study of animal models for affective disorders; mice are suspended by the tail from a lever, and the duration of movements (a period of agitation followed by immobility) is recorded. Antidepressant drugs prolong the active struggling. [4]

tail-flick test

Technique used to measure pain sensitivity in an animal by placing a beam of light on the animal’s tail and recording the time it takes for the animal to remove its tail from the beam. [4]

tar

Mixture of hydrocarbons created by the vaporization of nicotine in tobacco. Tar is a major component of cigarette smoke. [13]

tardive dyskinesia (TD)

Undesired response to antipsychotic drugs characterized by involuntary muscle movements, particularly of the face, head, and neck, that may be irreversible in some patients. [19]

Tasmar

See tolcapone. [5]

tau

Protein associated with NFTs. [20]

TCA

See tricyclic antidepressant. [18]

tegmentum

Division of the midbrain. The tegmentum is composed of several important structures including the PAG, substantia nigra, and the VTA. [2]

Tegretol

See carbamazepine. [18]

temporal lobe

One of four lobes of the cerebral cortex. It contains the auditory cortex and helps integrate auditory information. [2]

teratogen

Any agent including a virus, drug, or radiation that induces abnormal fetal development, causing birth defects. [1]

terminal autoreceptors

Autoreceptors that are located on axon terminals and that inhibit neurotransmitter release. [3]

terminal buttons

Small enlargements at the axon terminal, in close proximity to the dendrites of the postsynaptic cell, containing synaptic vesicles. Also known as boutons. [2]

tertiary association areas

Section of the cerebral cortex where the three sensory lobes can interact, providing a higher order of perception and memory. [2]

testes

Male specific gonads that secrete androgens. [3]

testosterone

The principal androgen (male sex steroid) secreted by the testes. [3]

tetanic stimulus

Electrical stimuli delivered repeatedly, in a brief train of electrical bursts. Also referred to as tetanus. [8]

tetanus

A train of electrical stimuli that is used experimentally to induce LTP. Also referred to as a tetanic stimulus. [8]

TH

See tyrosine hydroxylase. [5]

thalamus

Structure of the diencephalon that is responsible for processing and distributing sensory and motor signals to the appropriate section of the cerebral cortex. [2]

THC

See Δ⁹-tetrahydrocannabinol. [14]

theophylline

Stimulant drug similar to caffeine that is found naturally in tea. [13]

therapeutic drug monitoring

Taking multiple blood samples to directly measure plasma levels of a drug after administration, to identify the optimum dosage for maximum therapeutic potential and minimal side effects. [1]

therapeutic effects

Desired physical or behavioral changes associated with a particular drug. [1]

therapeutic index

The relationship between the drug dose that results in a toxic response compared to the dose required for the desired biological response. It is represented by the equation TI = TD₅₀/ED₅₀ where TD₅₀ is the dose that is toxic for 50% of the population and ED₅₀ is the effective dose for 50%. [1]

thiosemicarbazide

Drug that blocks GABA synthesis, inducing convulsions. [8]

threshold

Membrane potential, typically –50 mV, at which voltage-gated Na⁺ channels will open, generating an action potential. [2]

thyroid gland

Specific endocrine gland that is located in the throat and secretes T3 and T4. [3]

thyroid-stimulating hormone (TSH)

Hormone that stimulates the thyroid gland. It is secreted by the anterior pituitary. [3]

thyrotropin-releasing hormone (TRH)

Hormone that stimulates TSH release. It is synthesized by neurons of the hypothalamus. [3]

thyroxine (T4)

Hormone that is synthesized from tyrosine and helps control normal energy and metabolism in the body. It is secreted by the thyroid gland. [3]

tiagabine (Gabitril)

Drug that is a selective inhibitor of GAT-1. It is used in pharmacological studies and to treat patients with partial seizures who are resistant to standard antiepileptic drugs. [8]

tianeptine

Tricyclic antidepressant (TCA) that modulates glutamate function. [18]

tight junctions

Connection between cells characterized by a fusing of adjoining cell membranes. In cerebral capillaries, the lack of small gaps prevents the movement of molecules across the capillary wall unless the molecules are lipid soluble. [1]

tolcapone (Tasmar)

COMT inhibitor used in conjunction with l-DOPA to treat Parkinson’s disease. [5]

tolerance

Decreased response to a drug as a direct result of repeated drug exposure. [1, 10, 11, 12]

tonic release

Slow, consistent release of neurotransmitter that is typically associated with single-spiking mode of cell firing. It maintains low but relatively constant extracellular levels of the transmitter. [5]

topical

Method that involves administration of a drug through a mucous membrane such as the oral cavity, nasal mucosa, or vagina. [1]

TPH

See tryptophan hydroxylase. [6]

tracts

Bundles of nerve axons in the CNS sharing a common origin and target. [2]

transcription

Process whereby mRNA produces a complementary copy of an active gene. [2]

transcription factors

Nuclear proteins that regulate the rate of gene transcription within a cell. [2, 3]

transdermal

Method that involves administration of a drug through the skin (e.g., with a patch). [1]

transfection

Process used to introduce genetic material into a cell by injecting it with a DNA sequence coding for the desired protein product. [11]

transgenic mice

Mice bred to replace one gene with another (e.g., a normal gene with a mutant version of that gene). They are used to study genetic disorders. [4]

translation

Process whereby proteins are produced using the nucleotide sequence carried by mRNA to direct the amino acid sequence. Translation is performed by ribosomes. [2]

translational medicine

Process by which basic scientific findings (e.g., using animal models) increase the understanding of important disease processes and aid the development of new medical therapies. [8]

transporters

Specific proteins in the cell membrane that transport molecules into and out of the cell (e.g., proteins that remove neurotransmitters from the synaptic cleft following their release). They are sometimes called transporter proteins. [3]

tranylcypromine (Parnate)

MAO inhibitor used to treat clinical depression. [5]

TRH

See thyrotropin-releasing hormone. [3]

tricyclic antidepressants (TCAs)

Class of antidepressants characterized by a three-ring structure. They block reuptake of NE and 5-HT, thereby increasing their concentration in the synaptic cleft. [5, 18, 20]

triggers

Classically conditioned cues associated with drug taking that cause craving. [11]

trihexyphenidyl (Artane)

Anticholinergic drug used to treat early symptoms of Parkinson’s disease. [7]

triiodothyronine (T3)

Hormone that is synthesized from tyrosine and helps control normal energy and metabolism in the body. It is secreted by the thyroid gland. [3]

trinucleotide repeat

A form of mutation characterized by a stretch of three nucleotides (a codon) repeated in multiple times in the DNA sequence. [20]

TRPV1

Nonspecific cation channel receptor that was first discovered in sensory neurons where it plays a key role in the heat and pain sensations produced by capsaicin. Within the brain, TRPV1 receptors can be activated by anandamide. [14]

tryptophan

Amino acid characterized by the presence of an indole group. It is a precursor to 5-HT. [6]

tryptophan depletion challenge

Research method used to investigate the role of serotonin in depressive disorders, in which subjects consume a tryptophan-deficient amino acid cocktail that transiently reduces 5-HT level in the brain. [18]

tryptophan hydroxylase (TPH)

Enzyme that catalyzes the conversion of tryptophan into 5-HTP. [6]

tryptophan loading

Administration of pure tryptophan for the purpose of elevating blood tryptophan concentrations. [6]

TSH

See thyroid-stimulating hormone. [3]

tuberohypophyseal dopamine pathway

Pathway that controls the secretion of the hormone prolactin by the pituitary gland. [5]

twin studies

Studies used to understand how heredity contributes to a disorder by comparing the concordance rate for the disorder in pairs of monozygotic and dizygotic twins. [18]

type 2 diabetes

Disorder characterized by chronically elevated blood glucose levels. One form of the disorder is produced by insulin resistance, which means that ability of insulin to promote glucose uptake has become compromised. [7]

tyrosine

Amino acid characterized by a phenol group. It is necessary for the synthesis of the catecholamine neurotransmitters. [5]

tyrosine hydroxylase (TH)

Enzyme that catalyzes the first step of catecholamine synthesis in neurons, the conversion of tyrosine to DOPA. [5]

tyrosine kinase receptors

Family of receptors that mediate neurotrophic factor signaling. [3]

U

ultrafast endocytosis

Mechanism for extremely rapid retrieval of synaptic vesicle membrane components from the membrane of the axon terminal. [3]

ultrasonic vocalizations

High-frequency rodent calls typically emitted by juveniles as when separated from their mothers, indicating distress. [4]

up-regulation

Increase in the number of receptors, which may be a consequence of denervation or of chronic antagonist treatment. [1]

V

VaChT

See vesicular ACh transporter. [7]

vacuous chewing movements test

A technique used to evaluate the potential motor side effects of antipsychotic drugs. [19]

Valium

See diazepam. [8]

valproate (Depakote)

Simple branched-chain fatty acid that was the first anticonvulsant approved by the U.S. FDA for treatment of acute mania. [18]

vanillymandelic acid (VMA)

Metabolite of NE, formed primarily by NE breakdown in the peripheral nervous system. [5]

varenicline (Chantix)

Drug that is a partial agonist at high affinity α4β2 nAChRs. It is used in the treatment of tobacco dependence. [13]

varicosities

Repeated swellings of nerve fibers that contain large numbers of synaptic vesicles and that serve as sites of neurotransmitter release. The fibers of dopaminergic and noradrenergic neurons characteristically show varicosities in the brain areas or (in the case of norepinephrine) peripheral organs that they innervate. [5]

vasopressin

Peptide hormone secreted by the posterior pituitary that increases water retention by the kidneys. [3]

Ventolin

See albuterol. [5]

ventral

Located toward the underside of the brain or front of the body in humans. [2]

ventral tegmental area (VTA)

Region containing dopaminergic cell bodies within the tegmentum of the mesencephalon (midbrain) that form the mesolimbic and mesocortical tracts. [2, 5]

vesamicol

Drug that blocks the vesicular ACh transporter. [7]

vesicle recycling

Multi-step process consisting of removal of synaptic vesicle membrane components from the membrane of the axon terminal after exocytosis, followed by formation of new vesicles. [3]

vesicular ACh transporter (VAChT)

Vesicle membrane protein that transports ACh into synaptic vesicles. [7]

vesicular GABA transporter (VGAT)

Vesicle membrane protein that transports both GABA and glycine into synaptic vesicles; also known as VIAAT. [8]

vesicular glutamate transporter (VGLUT)

Vesicle membrane protein that transports glutamate into synaptic vesicles. There are three such proteins, designated VGLUT1 to VGLUT3, which differ in their location within the brain. [8]

vesicular inhibitory amino acid transporter (VIAAT)

See vesicular GABA transporter. [8]

vesicular monoamine transporter (VMAT)

Vesicle membrane protein that transports monoamines (i.e., catecholamines and 5-HT) into synaptic vesicles. Monoamine neurons express a particular form of VMAT called VMAT2, whereas the epinephrine- and norepinephrine-secreting chromaffin cells of the adrenal medulla express a different form called VMAT1. [5]

VGLUT

See vesicular glutamate transporter. [8]

VIAAT

See vesicular GABA transporter. [8]

Vigabatrin (Sabril)

Drug that irreversibly inhibits GABA-T. It is used to treat epilepsy. [8]

vilazodone (Viibryd)

Drug that blocks the 5-HT transporter and also acts as a 5-HT_1A receptor partial agonist. It is used to treat anxiety disorders and depression. [6]

viral vectors

Use of viruses as a delivery system (called a vector) to carry a gene into the nuclei of target cells to alter protein synthesis. [1]

VMA

See vanillymandelic acid. [5]

VMAT

See vesicular monoamine transporter. [5]

Vogel test

Water-lick suppression test (a conflict procedure) that reliably screens anxiety-reducing drugs in rodents. [4]

volatile solvents

Class of inhalants characterized by chemicals, such as adhesives, ink, and paint thinner, that are liquid at room temperature, but readily give off fumes that can be easily inhaled. [16]

voltage-gated channels

Type of ion channels that are regulated by voltage differences across the membrane. [2]

volume transmission

Phenomenon characterized by the diffusion of a chemical signal (e.g., a neurotransmitter) through the extracellular fluid to reach target cells at some distance from the point of release. [3]

VTA

See ventral tegmental area. [2, 5]

W

water-lick suppression test (Vogel test)

Technique used to measure anxiety in rodents by recording their propensity to lick a drinking spout that will also deliver a mild electric shock. Also called Vogel test. [4]

WAY 100635

Drug that selectively inhibits 5-HT_1A receptors. [6]

Western blot

A research method that uses antibodies to quantify a specific protein in a tissue homogenate. [4]

wiring transmission

Point-to-point communication between neurons in which the neurotransmitter acts locally within the synapse to affect the target cell. The opposite of wiring transmission is volume transmission. [3]

withdrawal syndrome

Rebound physiological state that occurs at drug cessation in an individual following chronic drug use. It is the defining element of physical dependence. [1]

withdrawal

See abstinence syndrome. [11]

X

Xyrem

See sodium oxybate. [16]

Y

yohimbine

α₂-antagonist that blocks autoreceptors and increases noradrenergic cell firing. It enhances symptoms of opioid withdrawal. [5]

Z

Zecuity

Transdermal (patch) form of sumatriptan that is used to treat migraine headaches. [6]

zero maze

Elevated donut-shaped platform used to measure anxiety in rodents. [4]

zero-order kinetics

Term used to describe a constant rate of drug removal from the body, regardless of drug concentration in the blood. [1]

zolmitriptan (Zomig)

Drug that stimulates 5-HT_1B/1D receptors, thereby causing constriction of cerebral blood vessels. It is used to treat migraine headaches. [6]

Zyban

See bupropion. [13]