Drugs of abuse: General/Cannabis

Question 1

What is the central reward pathway?

Answer 1

Collection of dopaminergic neurons originating in the ventral tegmental area and projecting down to the nucleus accumbens, where dopamine is released.

Question 2

What are the possible routes of administration of drugs of abuse?

Answer 2

Intranasal (snort)
Oral (eat)
Inhalational (smoke)
Intravenous (inject)

Question 3

How are drugs of abuse classified?

Answer 3

Narcotics/painkillers- opiate-like drugs, e.g. heroin
Depressants- ‘downers’, e.g. alcohol, barbiturates, benzodiazepines
Stimulants- ‘uppers’, e.g. cocaine, amphetamine, caffeine, nicotine
Miscellaneous, e.g. cannabis, ecstasy

Question 4

What percentage of orally administered cannabis enters the bloodstream?

Answer 4

5-15%

Delayed onset, slow absorption, first-pass metabolism.

Question 5

What percentage of inhalationally administered cannabis enters the bloodstream?

Answer 5

25-35%

Question 6

What is the major long-term storage site in the body of cannabis?

Answer 6

Cannabis is very lipid-soluble, and slowly accumulates in poorly perfused fatty tissues. Body fat is the major long-term storage site. Fatty acid conjugates build up in fatty tissue.

Question 7

How is cannabis excreted?

Answer 7

65% of excretion occurs via the GI tract in bile, subject to enterohepatic cycling.
25% of excretion is via urine.

Question 8

Where are CB1 receptors found?

Answer 8

Hippocampus
Cerebellum
Cerebral cortex
Basal ganglia

Question 9

Where are CB2 receptors found?

Answer 9

Immune cells

Question 10

How does cannabis cause euphoria?

Answer 10

Disinhibition of GABA neurons- stops suppression of the reward pathway, so more dopamine is released from the nucleus accumbens.

Question 11

What is the role of the anterior cingulate cortex, and how is it affected in cannabis users?

Answer 11

Error detection
Performance monitoring with behavioural adjustment to avoid losses.
Hypoactivity of ACC in cannabis users.

Question 12

What is the effect of cannabis on food intake?

Answer 12

Positive effect on orexigenic neurons in lateral hypothalamus.
Presynaptic inhibition of GABA increases MCH neuronal activity.
Increased orexin production.
Increased appetite.

Question 13

What effects can cannabis have on the body?

Answer 13

Euphoria
Psychosis, schizophrenia
Increased food intake
Memory loss- limbic regions
Psychomotor performance- cerebral cortex
Immunosuppression
Tachycardia/vasodilation

Question 14

What is dronabinol used to treat?

Answer 14

Nausea and vomiting in chemotherapy patients

Loss of appetite and weight loss in AIDS patients