L8 : DRUG USE, DRUG ADDICTION AND THE BRAIN REWARDS CIRCUITS

Question 1

Sensitisation

Answer 1

after prolonged exposure, need less of it for same level of effect (classically amphetamines and cocaine)

Question 2

tolerance

Answer 2

need more to get the same effect

Question 3

withdrawal

Answer 3

physiological reaction to a lack of the addictive substance

Question 4

conditioned drug tolerance

Answer 4

maximal tolerance effects are seen in the environment in which a drug is usually taken, often with heroin users

Question 5

contingent drug tolerance

Answer 5

tolerance only develops to drug effects that are experienced, e.g. if you don’t walk whilst drinking, but then drink and walk you don’t have tolerance to the effect of alcohol on walking

Question 6

ingestion

Answer 6

Easy and relatively safe
Absorption via digestive tract is unpredictable

Question 7

injection- bypass digestive tract

Answer 7

Subcutaneously (sc) under the skin
Intramuscularly (IM) into large muscles
Intravenously- into veins, direct to brain- gets to brain extremely quickly (less of a gap needed for operant conditioning- temporal concordance)

Question 8

inhalation

Answer 8

absorbed through capillaries in lungs
Absorption through mucous membrane- nose, mouth
Crack-cocaine more addictive as it gets to brain more quickly when smoked

Question 9

how nicotine works

Answer 9

Binds to nicotinic acetylcholine receptors
Acetylcholine- links all over the neocortex, nucleus basalis projects to neocortex, pedunculopontine nucleus projects to thalamus- has alertness effects

Question 10

how cocaine and amphetamine increase DA

Answer 10

Block reuptake of DA and so leave more for the synapse for the receptor
Dopamine are at the bottom of the brain; the substantia nigra, ventral tegmental area that goes up to the nucleus accumbens and the prefrontal neocortex (at the dopaminergic terminals)

Question 11

MDMA and serotonin synapses

Answer 11

Blocks reuptake and also reverses reuptake transporter, increasing serotonin in synaptic cleft
Serotonergic projections- all over the brain
LSD - binds to serotonin receptors, interferes with sleep-waking systems

Question 12

caffeine binds to

Answer 12

adenosine receptors

Question 13

cannabis

Answer 13

THC primary psychoactive consititutent, bind to cannabinoid receptors

Question 14

alcohol

Answer 14

inhibitory- potential actions of GABA

Question 15

OPIATES: morphine and heroin

Answer 15

bind to opiod receptors, analgesics (painkillers), activate pain blocing neurons in spinal cord

Question 16

how investigate drug use

Answer 16

Self report- questionnaires e.g. fagerstrom test for nicotine
Animal models- e.g. behavioural preference tests (conditioned place preference- rat in a drug and non-drug compartment), intr-cranial self stimulation (press lever for direct stimulation of brain or lever for drugs), self administration paradigm (infusion pump implanted in rat, will rat press lever)

Question 17

why doe we take drugs

Answer 17

highjack brain reward systems

Question 18

fMRI

Answer 18

shows dopaminergic brain region becoms activated by nice things, cocaine, amphetamines and heroin all work on DA

Question 19

what does nicotine bind to and how does that relate to DA

Answer 19

binds to acetylcholine but also receptors on the ventra tegmental area that activates dopamine

Question 20

alcohol and da

Answer 20

inadvertently turns dopaminergic neurons on

Question 21

caffeine and cannabis DA

Answer 21

lots of receptors by the nucleus accumbens