Chapter 9: Drug Abuse and Addiction

Question 1

How do recent conceptions view drug addiction?

Answer 1

As a chronic, relapsing disorder characterized by repeated periods of remission followed by relapses.

Question 2

What are the two types of progression in drug use?

Answer 2

1. gateway theory

2. cycles of pathological drug use

Question 3

Explain the gateway theory of drug use.

Answer 3

Young people often progress from legal substances like alcohol or tobacco to marijuana and other drugs like cocaine, heroin, or illegally obtained prescription drugs. This theory explains this progression of drug use.

Question 4

How do cycles of pathological drug use lead to addiction?

Answer 4

These cycles have 3 components: 1) preoccupation-anticipation of upcoming drug use, 2) binge-intoxication, and 3) withdrawal-negative affect in the periods following drug use.

Repeated cycles can cause spiraling distress and eventually lead to addiction. Additional features of the cycle include taking drugs in larger amounts than intended, developing tolerance (and related withdrawal symptoms), compromised functioning in daily activities, and spiraling distress.

Question 5

What is the Schedule of Controlled Substances?

Answer 5

It is a system that classifies most substances with abuse potential into one of five schedules based on their degree of abuse potential and medicinal value. Schedules I and II have the strictest guidelines. Alcohol and tobacco are excluded which allows them to se purchased and used legally without registration or prescription.

Question 6

Explain the relationship between drugs and reinforcement.

Answer 6

Most abused drugs exert rewarding and reinforcing effects. Drug reward is the positive subjective experience associated with the drug (e.g. a “high”). Reinforcement means that using the drug strengthens the behaviour that was performed before consuming the drug (learning model). Sometimes drug produce aversive effects but they may not be strong enough to outweight the other factors that contribute to developing and maintaining use.

Question 7

How is the reinforcing efficacy of drugs studied?

Answer 7

With animals trained to do IV self-administration:

1. dose-response function
2. breaking point determination using a progressive-ratio schedule
3. reinstatement of drug seeking behaviour

Question 8

What is the dose-response function?

Answer 8

When the drug is delivered using a simple schedule of reinforcement such as a fixed-ratio schedule, the typical dose-response function is an inverted U-shape curve. The ascending part of the curve reflects increasing reinforcing effectiveness of the drug and the descending limb represents satiation to the drug, aversive reactions, or behaviourally disruptive side effects.

Question 9

What is a progressive-ratio schedule?

Answer 9

Animals are initially trained to perform an operant response (e.g. lever pull) and administer the drug on a continuous reinforcement schedule (drug after every press). In phase 2, the reinforcement schedule changes to a low fixed-ratio. Then the fixed-ratio is progressive increased until the animals stop responding. They stop because the dose of the drug delivered is not rewarding enough for the effort required.

It is the preferred measure of the relative strength of drug reinforcement.

Question 10

What is the breaking point?

Answer 10

The response ratio at which the animal stops responding (ie. the operant response such as lever pulling).

Question 11

What is drug priming?

Answer 11

Delivery of a small dose of a drug by the experimenter for the purpose of eliciting drug-seeking behaviour, typically in an animal whose drug self-administration responding was previously extinguished.

Question 12

What is reinstatement of drug-seeking behaviour?

Answer 12

It is a procedure for modeling relapse in animals. Drug delivery is stopped forcing extinction of the operant response. Then the animal is exposed to stimuli that are known to provoke renewed responding (drug-seeking behaviour) in an attempt to obtain the drug again.

Question 13

What are the three main stimuli used to reinstate drug-related responding?

Answer 13

1. drug priming
2. subjecting the animal to stress
3. exposing the animal to environmental cues that were originally paired with drug delivery

Question 14

What procedures are used to study the rewarding properties of drugs?

Answer 14

1. place conditioning

2. electrical self-stimulation

Question 15

What is place conditioning

Answer 15

A classical conditioning procedures where animals are trained in an apparatus with two or three compartments. One of the comparements is paired with the drug and the others with a placebo. Under drug-free conditions the animal will spend more time in this compartment if the effects of the drug were rewarding and less time in it if they were aversive.

Question 16

What is electrical self-stimulation?

Answer 16

A procedure where the performance of an operant response causes the delivery of an electrical stimulus to a part of the brain’s reward circuit.

Question 17

What are the key findings about drugs of abuse and electrical self-stimulation?

Answer 17

When animals have been treated acutely with drugs of abuse, the threshold for rewarding brain stimulation is reduced (i.e. the system is more sensitive). Withdrawal from chronic treatment of drugs of abuse increases the threshold for brain stimulation.

Question 18

What is the role of physical dependence in the maintenance of drug abuse?

Answer 18

Physical dependence plays a role in maintenance of drug abuse for some substances. When physical dependence has developed, the individual experiences highly unpleasant withdrawal symptoms when they do not use the drug.

Question 19

What is the role of discriminative stimulus effects in the drug-seeking behaviour?

Answer 19

Some drugs have the ability to produce internal states in the organism that act as cues influencing their behaviour. Experienced drug users expect subjective effects from using a particular drug and these expectations contribute to persistence in seeking and using the drug.

Question 20

Describe the physical dependence model of addiction?

Answer 20

Stage 1: Impulsive stage
The main motivation for drug use is the positive reinforcing effects. Individuals go through the cycle of 1) intoxication/binge, 2) pleasurable effects, 3) abstinence and neutral effect, and 4) reward craving. The individual develops a physical dependence to the drug with repeated use and moves to the compulsive stage.

Stage 2: Compulsive stage
Abstinence from drug use has a negative effect (withdrawal symptoms) because of the physical dependence. Individuals are motivated to use the drug to relieve withdrawal symptoms. The cycle is: 1) prolonged intoxication, 2) relief, 3) protracted abstinence and negative affect, and 4) relief craving.

Question 21

What role does conditioning have in withdrawal?

Answer 21

Through conditioning, environmental stimuli previously associated with drug use can elicit withdrawal symptoms (e.g. drug craving) in an abstinent individual.

Question 22

What is the link between genetics and addiction?

Answer 22

Addiction is a heritable disorder, but there is no addiction gene per se. Instead, specific alleles of many different genes contribute a small increase in the risk for developing addiction.

Question 23

How are the genetics of neuropsychiatric disorders studied?

Answer 23

1. candidate gene analysis
2. linkage analysis
3. genome-wide association studies

Question 24

What are protective factors against addiction?

Answer 24

1. not having a preexisting personality or mood disorder
2. stable family with no history of substance abuse
3. not belonging to ethnic groups that promote substance use
4. not becoming involved with social rituals surrounding drug use

Question 25

What are risk factors for addiction?

Answer 25

1. personality variables (e.g. impulsivity, antisociality)
2. suffering from anxiety, mood or personality disorders
3. familial influences
4. sociocultural influences

Question 26

What is the biopsychosocial model of addiction?

Answer 26

Combined pharmacological, biological, psychological/sociocultural factors to give a full account of addiction.

Question 27

Explain natural recovery.

Answer 27

Recovery from drug addiction without treatment. It may be facilitated by transitional life events and/or by the negative consequences of drug use. The likelihood of achieving natural recovery is lower for severely affected substance users.

Question 28

What are the 5 key anatomical pathways within the reward circuit?

Answer 28

1. Mesolimbic dopamine pathway
2. Mesocortical dopamine pathway
3. Extended amygdala circuit
4. Medial forebrain bundle
5. Output pathway from the nucleus accumbens to the ventral pallidum

Question 29

Explore the role of the mesolimbic dopamine pathway in drug reward.

Answer 29

It originates in the ventral tegmental area and terminates in the nucleus accumbens and amygdala. Almost all drugs of abuse activate the pathway from the ventral tegmental area to the NAcc. They work by elevating extracellular dopamine either by enhancing VTA cell firing or acting locally to release DA from nerve terminals or block its reuptake. this mimics the effect of burst firing.

Question 30

Explain incentive sensitization theory.

Answer 30

Repeated drug use leads to an incease in “wanting” the drug (i.e. craving) but no increase in drug “liking” (reward) because only the neural system underlying drug “wanting” becomes sensitized.

Question 31

What neuroadaptations result from repeated drug use?

Answer 31

1. Within-system: progressive down-regulation of the reward system
2. Between-system: recruitment of an antireward circuit that mediates the withdrawal/negative affect stage

Question 32

What is the extended amygdala circuit?

Answer 32

The extended amygdala circuit consists of the central nucleus of the amygdala, the shell of the nucleus accumbens, and the bed nucleus of the stria terminalis. The structures in the circuit are anatomically and functionally linked.

Question 33

How does the antireward system work?

Answer 33

It is centered around the extended amygdala circuit. It is activated during stress and drug withdrawal. Activating the circuit results in increased release of NE, CRF, and dynorphin.

Question 34

What is the opponent-process model of addiction?

Answer 34

Early drug use is motivated primarily by positively reinforcing effects (reward circuit), whereas later drug use (after addiction has taken place) is motivated primarily by negative reinforcement produced by alleviation of aversive withdrawal symptoms (antireward system).

Question 35

What are the neural mechanisms of the preoccupation-anticipation stage?

Answer 35

1. Intrusive thinking, drug craving and lack of control = dysregulation of the PFC and descending glutamatergic projections to the striatum and other subcortical structures
2. Cue-induced craving = activates the insula
3. Loss of control over drug use = transition of behavioural control from ventral striatum to the dorsal striatum
4. Increased impulsivity = blunted striatal DA transmission due to reduced DA release and lower D2 receptor binding

Question 36

What are epigenetic effects of drug use?

Answer 36

1. prime a gene to be expressed more strongly or repressed upon later drug administration
2. epigenetic changes from ACEs may increase the risk for future addiction
3. epigenetic modifications to parents’ genes may by transmitted to offspring