Science of Addiction

Question 1

What are the 2 distinct mechanisms underlying substance misuse?

Answer 1

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Question 2

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

What is tolerance defined as?

Answer 2

“Reduced responsiveness to a drug caused by previous administration”

Question 3

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Tolerance is “Reduced responsiveness to a drug caused by previous administration”

Tolerance develops in response to many types of drug. Give examples.

Answer 3

• opioids
• ethanol
• barbiturates
• benzodiazepines

Question 4

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Tolerance is “Reduced responsiveness to a drug caused by previous administration”

Tolerance is an example of which physiological phenomenon?

Answer 4

An example of homeostasis.

• the body likes things the way they were

•Mechanisms underlying tolerance can vary

Question 5

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Tolerance is “Reduced responsiveness to a drug caused by previous administration”

What are the 2 mechanisms of tolerance?

Answer 5

1. Dispositional tolerance
2. Pharmacodynamic tolerance

Question 6

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Tolerance is “Reduced responsiveness to a drug caused by previous administration”

There are 2 mechanisms of tolerance;

1. Dispositional tolerance
2. Pharmacodynamic tolerance

What is dispositional tolerance?

Answer 6

less drug reaches the active site, eg

• decreased rate of absorption
• increased rate of metabolism to inactive metabolites
• decreased rate of metabolism to active metabolites
• increased rate of excretion

Question 7

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Tolerance is “Reduced responsiveness to a drug caused by previous administration”

There are 2 mechanisms of tolerance;

1. Dispositional tolerance
2. Pharmacodynamic tolerance

The development of tolerance may lead to?

Answer 7

Withdrawal symptoms should the drug be stopped due to;

• Adaptive response e.g. increased sensitivity to transmitter

Question 8

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Tolerance is “Reduced responsiveness to a drug caused by previous administration”

There are 2 mechanisms of tolerance;

1. Dispositional tolerance
2. Pharmacodynamic tolerance

The development of tolerance will lead to withdrawal effects.

What is the withdrawal effect of opioids?

Answer 8

–withdrawal effect of a drug is usually the reverse of the acute effect

Opioids

Acute = Constipation

Withdrawal = Diarrhoea

Question 9

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Tolerance is “Reduced responsiveness to a drug caused by previous administration”

There are 2 mechanisms of tolerance;

1. Dispositional tolerance
2. Pharmacodynamic tolerance

The development of tolerance will lead to withdrawal effects.

What is the withdrawal effect of barbituates?

Answer 9

–withdrawal effect of a drug is usually the reverse of the acute effect

Barbituates

Acute = Anticonvulsant

Withdrawal = Convulsions

Question 10

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

Tolerance is “Reduced responsiveness to a drug caused by previous administration”

There are 2 mechanisms of tolerance;

1. Dispositional tolerance
2. Pharmacodynamic tolerance

The development of tolerance will lead to withdrawal effects.

What is the withdrawal effect of Cocaine?

Answer 10

–withdrawal effect of a drug is usually the reverse of the acute effect

Cocaine

Acute = Elevated mood

Withdrawal = Depressed mood

–Tolerance & dependence are closely linked

–Development of tolerance may lead to physical dependence in order to avoid the (unwelcome) withdrawal effects

Question 11

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

What is the reward pathway?

Answer 11

• Neurones project from the ventral tegmental area to the nucleus accumbens & prefrontal cortex
• When VTA neurones are stimulated they release dopamine is released
• This causes a sensation of pleasure/reward

Question 12

The 2 mechanisms underlying drug misuse are;

1. Tolerance (the basis of physical dependence)
2. Reward centre (the basis of psychological craving)

The reward pathway is;

• Neurones project from the ventral tegmental area to the nucleus accumbens & prefrontal cortex
• When VTA neurones are stimulated they release dopamine is released
• This causes a sensation of pleasure/reward

Some drugs of abuse tap into the reward pathway and increase dopamine levels. Give examples

Answer 12

–heroin increases firing rate of dopaminergic neurones

–amphetamine increases dopamine release

–cocaine inhibits dopamine uptake

–alcohol

This produces the psychological component of addiction - “craving”