Addiction

Question 1

what is the reward pathway in the brain

Answer 1

ventral tegmental area (VTA) stimulation leads to release of dopamine from nucleus accumbens (NAcc)

Question 2

what are the pharmacokinetics of cannabis

Answer 2

cannabis binds to CB1 on neurones and suppresses GABA release leading to VTA stimulation

heavily affected by first pass metabolism
very lipid soluble - peaks in fat 5 days after administration
65% is excreted in the liver therefore leads to enterohepatic recycling
CB1 receptors in brain - hippocampus, cerebellum, cerebral cortex, basal ganglia
CB2 receptors on immune cells

Question 3

what are the pharmacokinetics of nicotine

Answer 3

binds to nicotinic ACh receptors and causes stimulation of VTA
broken down in liver 
half life 1-4hrs
similar cardiac effects as cocaine 
increases metabolic rate

Question 4

what are the pharmacokinetics of cocaine

Answer 4

blocks dopamine reuptake transporter so increases amount of dopamine in neuronal cleft

half life 20-90 minutes
local anaesthetic - blocks Na pumps
similar cardiac effects as nicotine - strong link to head damage

Question 5

what are the pharmacokinetics of alcohol

Answer 5

primarily acts as depressant - enhances GABA production which increases dopamine
metabolised in the liver - alcohol dehydrogenase converts alcohol to acetaldehyde (toxic), the acetaldehyde dehydrogenase converts it to acetic acid

Question 6

what are the mechanisms of tolerance

Answer 6

receptor internalisation
tissue tolerance
tissue up regulated arrestin