14-Drug Use, Drug Addiction, and the Brain's Reward Circuits

Pharmacological

pertaining to the scientific study of drugs

Psychoactive drugs

drugs that influence subjective experience and behavior by acting on the nervous system

1. Oral Ingestion

2. Injection

3. Inhalation

4. Absorption through the mucuos membranes of the nose, mouth, or rectum

routes of administration

Routes of administration

influences the rate at which and the degree to which the drug reaches its sites of action in the body

Oral ingestion

is the preferred route

of administration for many drugs

Oral ingestion

Once they are swallowed,

drugs dissolve in the fluids of the stomach and are

carried to the intestine, where they are absorbed into the

bloodstream.

metabolites

Drugs that are not readily absorbed from

the digestive tract or that are broken down into inactive

intestine

some drugs readily pass through

the stomach wall (e.g., alcohol), and these take effect

sooner because they do not have to reach the - to

be absorbed

Injection

common in medical practice

because the effects of injected drugs are strong, fast,

and predictable.

1. Subcutaneously (SC)

2. Intramuscularly (IM)

3. Intravenously (IV)

Drug injections routes

Subcutaneously (SC)

into the fatty tissue just beneath the skin

Intramuscularly (IM)

into the large muscles

Intravenously (IV)

directly into veins at points where they run just

beneath the skin

Intravenously (IV)

Many drug-addicted persons prefer the

- because the bloodstream delivers the

drug directly to the brain

Inhalation

Some drugs can be absorbed into the

bloodstream through the rich network of capillaries in

the lungs.

Cocaine

is commonly self-administered through the nasal

membranes (snorted)—but not without damaging them

Blood-brain barrier

Once a drug enters the bloodstream, it is carried to

the blood vessels of the central nervous system. Fortunately,

a protective filter, the - makes it difficult for many potentially dangerous bloodborne

chemicals to pass from the blood vessels of the CNS into the

extracellular space around CNS neurons and glia.

Drug metabolism

These liver enzymes stimulate the conversion of

active drugs to nonactive forms—a process referred to as -

Liver

The actions

of most drugs are terminated by enzymes synthesized by

the -

Drug metabolism

eliminates

a drug’s ability to pass through lipid membranes

of cells so that it can no longer penetrate the blood–brain

barrier.

Drug tolerance

is a state of decreased

sensitivity to a drug that develops as a result of

exposure to it.

Dose-response curve

a graph of the magnitude of the effect

of different doses of the drug

Cross tolerance

One drug can produce tolerance to other drugs that

act by the same mechanism

Drug sensitization

Increasing sensitivity to a drug is called

Metabolic tolerance

Drug tolerance that results from

changes that reduce the amount of the drug getting to its

sites of action is called

Functional tolerance

Drug tolerance

that results from changes that reduce the reactivity of the

sites of action to the drug is called

Withdrawal syndrome

After significant amounts of a drug

have been in the body for a period

of time (e.g., several days), its

sudden elimination can trigger an

adverse physiological reaction

called a -

Drug withdrawal

Symptoms of a - are virtually

always opposite

to the initial effects of the drug.

physically dependent

Individuals who

suffer withdrawal reactions when

they stop taking a drug are said

to be - on

that drug.

Drug-addicted individuals

are those habitual

drug users who continue to use a drug

despite its adverse effects on their health

and social life, and despite their repeated

efforts to stop using it.

Contingent drug tolerance

refers to

demonstrations that tolerance develops

only to drug effects that are actually

experienced

Before-and-after design

Most studies of contingent

drug tolerance employ the -

Conditioned drug tolerance

refers to demonstrations that tolerance effects are

maximally expressed only when a drug is administered in

the same situation in which it has previously been administered

situational specificity of drug tolerance

tolerance was observed only when the

rats were injected in the environment that had previously

been paired with alcohol administration

Conditioned compensatory responses

The central assumption of the theory

is that conditional stimuli that predict

drug administration come to elicit conditional

responses opposite to the unconditional

effects of the drug.

exteroceptive stimuli

Most demonstrations of conditioned drug tolerance have

employed

exteroceptive stimuli

external, public stimuli,

such as the drug-administration environment

interoceptive stimuli

it indicates that just thinking about a

drug can evoke conditioned compensatory responses.

Nicotine

the major psychoactive

ingredient of tobacco

Tar

some 4,000 other chemicals,

collectively referred to as -, are absorbed through the

lungs

Drug craving

an affective

state in which there is a strong desire for the drug

Smoker’s syndrome

is characterized by chest pain,

labored breathing, wheezing, coughing, and a heightened

susceptibility to infections of the respiratory

tract.

Bronchitis

chronic inflammation

of the bronchioles of the lungs

Emphysema

loss of elasticity of the lung from chronic irritation

Buerger’s disease

mostly in male smokers—the blood vessels, especially

those supplying the legs, become constricted.

Teratogen

an agent that can disturb the normal development

of the fetus

depressant

Alcohol is classified as a - because at moderate-to-high doses it depresses

neural firing; however, at low doses, it can stimulate neural

firing and facilitate social interaction

diuretic

Alcohol is also a -;

that is, it increases the production of urine by the kidneys.

Hangover

Withdrawal from alcohol, even

after a single bout of drinking, can produce a withdrawal

syndrome of headache, nausea, vomiting, and tremulousness,

which is euphemistically referred to as a -

Tachycardia

rapid heartbeat

first phase of alcohol syndrome withdrawal

begins 6 to 8 hours after the cessation of alcohol

consumption and is characterized by anxiety, tremor,

nausea, and tachycardia

second phase of alcohol syndrome withdrawal

begins 10 to 30 hours after

cessation of drinking, and is characterized

by hyperactivity, insomnia, and hallucinations

third phase of alcohol syndrome withdrawal

the defining feature of the phase which typically occurs

between 12 and 48 hours after cessation of drinking, is

convulsive activity

delirium tremens (DTs)

fourth phase of alcohol syndrome withdrawal which usually begins

3 to 5 days after the cessation of drinking and lasts up to a week, is called

delirium tremens (DTs)

characterized by disturbing hallucinations, bizarre

delusions, disorientation, agitation, confusion, hyperthermia

(high body temperature), and tachycardia.

Korsakoff’s syndrome

alcohol indirectly causes -, characterized by memory

loss, sensory and motor dysfunction, and, in its advanced

stages, severe dementia, by inducing thiamine deficiency.

cirrhosis

Chronic alcohol consumption also causes extensive

scarring, or -, of the liver, which is the major

cause of death among heavy alcohol users.

Pancreatitis

inflammation of the pancreas

Gastritis

inflammation of the stomach

Fetal alcohol syndrome (FAS)

The offspring of mothers who consume substantial

quantities of alcohol during pregnancy can develop

Fetal alcohol syndrome (FAS)

suffers from some or all of the following

symptoms: brain damage, intellectual disability poor coordination,

poor muscle tone, low birth weight, retarded

growth, and/or physical deformiTY

Cannabis

Marijuana is the name commonly given to the dried flower

buds of -

1. Cannabis sativa

2. Cannabis indica

3. Cannabis ruderalis

cannabis species

joint

a cigarette of marijuana

delta-9- tetrahydrocannabinol (THC)

The psychoactive effects of marijuana are largely

attributable to a constituent called

cannabinoids

chemicals of the same chemical

class as THC

THCV (delta-9-tetrahydrocannabivarin)

cannabinoid that has been shown to have antipsychotic effects

China

Written records of Cannabis use go back 6,000 years in

-, where its stems were used to make rope, its seeds

were used as a grain, and its leaves and flowers were used for their psychoactive and medicinal effects

Middle Ages

In the -, cannabis cultivation spread into Europe, where it was

grown primarily for the manufacture of rope

George Washington

- was one of the more notable cannabis growers.

Narcotic

a legal term generally used to refer to opioids

Anandamide

The first endocannabinoid neurotransmitter to

be isolated and characterized was named - from a word that means “internal

bliss”

Glaucoma

THC has also been shown to decrease the severity of

- (a disorder characterized by an increase in the

pressure of the fluid inside the eye);

Sativex

mouth spray

that contains THC and other cannabinoids, was introduced

into several countries for the treatment of multiple sclerosis

symptoms

Stimulants

are drugs whose primary effect is to produce

general increases in neural and behavioral activity

Cocaine

is prepared from the leaves of the coca shrub,

which grows primarily in western South America.

coca paste

For centuries, a crude extract called - has been made

directly from the leaves and eaten

cocaine hydrochloride

Today, it is more

common to treat the coca paste and extract -,

the nefarious white powder that is referred to

simply as cocaine and typically consumed by snorting or

by injection

Crack

The impure residue of

this process is -, a potent, cheap, smokeable form of

cocaine.

Cocaine hydrochloride

is an effective local anesthetic

and was once widely prescribed as such until it was

supplanted by synthetic analogues such as procaine and

lidocaine.

Cocaine sprees

Individuals who are addicted to cocaine tend to go on

so-called -, binges in which extremely high

levels of intake are maintained for periods of a day or two

Cocaine psychosis

effects. The effects of cocaine

sprees include sleeplessness, tremors,

nausea, hyperthermia, and, in rare cases, psychotic

symptoms, which is called -

Amphetamine

its relatives are currently the most

widely misused stimulants

d-amphetamine (dextroamphetamine).

Amphetamines usually consumed orally in the potent form called

-

amphetamine psychosis

Some of the effects

of d-amphetamine are comparable to those of cocaine; for

example, it can also produce a syndrome of psychosis called -

methamphetamine (meth)

which is commonly used in its even more potent,

smokeable, crystalline form (crystal meth).

3,4-methylenedioxymethamphetamine (MDMA, or ecstasy),

Another potent relative of amphetamine is -, which is taken

orally

Emphatogens

are psychoactive

drugs that produce feelings of empathy

Dopamine transporters

The primary mechanism by which cocaine and its

derivatives exert their effects is by altering the activity

of -, molecules in the presynaptic

membrane that normally remove dopamine from synapses

and transfer it back into presynaptic neurons

Opium

the dried form of sap exuded by the seedpods of

the opium poppy

Morphine and codeine

some psychoactive ingredients of opium

Opiods

Morphine, codeine, and other drugs that have similar

structures or effects are commonly referred to as

endorphins and enkephalin

The endogenous opioid neurotransmitters that bind to

such receptors are of two classes

Analgesics

painkillers

laudanum

very popular mixture of opium and alcohol

carminative

is a drug that expels gas from the digestive

tract, thereby reducing stomach cramps and flatulence.

Harrison Narcotics Act

made

it illegal to sell or use opium, morphine, or cocaine in

the United States—although morphine and its analogues

are still legally prescribed for their medicinal properties.

Heroin

was synthesized in 1870 by the addition of

two acetyl groups to the morphine molecule, which greatly

increased its ability to penetrate the blood–brain barrier

rush

The effect of opioids most valued by users is the -

that follows intravenous injection

Heroin rush

wave of intense abdominal, orgasmic pleasure that evolves

into a state of serene, drowsy euphoria.