6.1. Addictions Symposium - Basic Science of Substance Misuse

Question 1

What are the 2 Distinct Mechanisms of Substance Misuse?

Answer 1

1. Tolerance - The Basis of Physical Dependence

2. Reward Centre - The Basis of Physiological Craving

Question 2

What is the Definition of Tolerance?

Answer 2

Reduced Responsiveness to a Drug caused by Previous Administration

Question 3

What can we develop Tolerance to?

Answer 3

1. Opioids
2. Alchohol (Ethanol)
3. Barbiturates
4. Benzodiazepines
   Note - The Mechanism underlying Tolerance can vary

Question 4

What are the Methods of Tolerance?

Answer 4

1. Dispositional Tolerance - Drug reaching Active Site:
2. a) Less Drug Absorbed
3. b) Drug Metabolised Faster to Inactive Metabolites
4. c) Drug Metabolised Slower to Active Metabolites
5. d) More Drug Excreted
6. Pharmacodynamic Tolerance - Action at the Active Site:
7. a) Fewer Drug receptors
8. b) Les Efficient Drug Receptors

Question 5

What can Tolerance lead to?

Answer 5

Development of Tolerance may lead to Withdrawal Symptoms

Question 6

What is the Mechanism of Tolerance Development leading to Withdrawal Symptoms?

Answer 6

1. Normal Synaptic Transmission = Normal Response
2. Drug Effect = Reduced Response
3. Development of Drug Tolerance = Normal Response
4. Drug Withdrawal = Increased Response

Question 7

What is the Normal Withdrawal effect of the Drug?

Answer 7

The opposite of the acute effects:

1. Opioid - Acute effect = Constipation / Withdrawal effect = Diarrhoea
2. Barbiturate - Acute effect = Anticonvulsant / Withdrawal effect = Convulsions
3. Cocaine - Acute effect = Elevated Mood / Withdrawal effect = Depressed mood

Question 8

What is the Reward Pathway?

Answer 8

1. Neurons prject from the Ventral Tegmental Area to the Nucleus Acumbens and Prefrontal Cortex
2. When the Ventral Tegmental Area is Stimulated Dopamine is Released
3. Dopamine causes a sensation of Pleasure / Reward

Question 9

When is the Reward Centre Activated?

Answer 9

1. Eating
2. Drinking
3. Sex
   It Encourages Healthy Behaviours

Question 10

How do Drugs act on the Reward Centres?

Answer 10

They tap in and increase Dopamine Levels:
1. Heroine increases Firing Rate of Dopaminergic Neurons
2. Amphetamine Increases Dopamine Release
3. Cocaine inhibits Dopamine uptake
4. Alcohol
Note - This produces the Psychological Component of Addiction - Craving