3.11 Neurobiology of Addiction

Question 1

What are the ICD-10 Criteria for “Dependence”?

Answer 1

1. Strong desire
2. Difficulties controlling
3. Physiological withdrawal
4. Tolerance
5. Neglect other pleasures
6. Persist despite evidence of harm

Question 2

What does CAGE stand for in addiction assessment?

Answer 2

C- Cut down
A- Annoyed
G- Guilty
E- Eye opener

Question 3

What three parts of the brain are particularly in the reward pathway?

Answer 3

1. Prefrontal cortex
2. Nucleus accumbens
3. Ventral tegmental Area

Dopaminergic activity in this mesolimbic pathway is motivating, incentivising, and is involved also in normal pleasurable experiences.

Question 4

Rats will stumulate which 2 areas of the brain to the exclusion of food/sex/water and accept pain until they starve to death?

Answer 4

1. VTA- Ventral tegmental area
2. NA- Nucleus accumbens

These behaviours can be blocked with dopamine ANTAGONISTS

Question 5

What is the change compared to controls in D2 receptors in addiction?

Answer 5

D2 dopamine receptors are decreased by addiction.

This may be linked to increased tolerance to reward

Question 6

What is the role of the Orbito-frontal cortex?

What changes can be seen in addiction?

Answer 6

The orbitofrontal cortex provides internal representations of events and their values.
It motivates actions.

In addicts, there is increased activation of the OFC when presented with drug cues. Hyperactivity of OFC correlated to cravings of drugs following cues.

Overall changes persist in OFC after abstinence.

Question 7

What is the general role of the prefrontal cortex?

Answer 7

Guides behaviour 
Modulates reward pathway
Sets goals
Focuses attention 
Makes sound decisions
Keeps emotions and impulses under control to achieve long term goals

Question 8

What is the order of frontal lobe maturation?

Answer 8

Back to front through the frontal lobe.

1. Primary motor cortex
2. superior and inferior frontal gyri
3. Prefrontal cortex

Question 9

What does dopamine release do in the pre-frontal cortex?

Answer 9

Dopamine release affects:

• ability to update info within PFC
• ability to set new goals
• ability to avoid compulsive repetitive behaviour

DRUGS disrupt the normal dopamine related learning in the prefrontal cortex.

Question 10

What are the roles of the following in addiction:

1. Striatum
2. Hippocampus

Answer 10

Striatum- habit learning
Hippocampus- Declarative learning

Also the amygdala, are critical in acquisition, consolidation, and expression of drug stimulus learning. They trigger craving.

Question 11

What % of addiction risk is due to genetic factors?

Answer 11

40-60%
This is the most heritable complex psychiatric condition.

• metabolic response
• behavioural traits predisposing
• rewarding sensation from drugs
• Receptor levels- Low DRD2 = higher risk

Question 12

What neurochemical event follows acute stress in the dependent individual?

Answer 12

Release of dopamine in the neural reward pathway- that can motivate drug seeking.

Question 13

What is the effect of chronic stress in the dependent individual?

Answer 13

Dampening of dopaminergic activity via downregulation of D receptors

= reduced sensitivity to normal rewards

Question 14

What does the pre-frontal cortex do in the reward circuit?

Answer 14

Puts the brakes on the reward pathway.

It is dysfunctional in addicted people.