lecture 15 LOs

Question 1

what system do all drugs of abuse w high addictive potential activate either directly or indirectly

Answer 1

mesolimbic dopamine system

Question 2

drugs of abuse activate the brains ____, but can do so to a much ____ degree

Answer 2

natural reward pathways, greater

Question 3

what does a drug being a positive reinforcer mean

Answer 3

consuming the drug strengthens whatever preceding behaviour was performed

Question 4

what does drug reward refer to

Answer 4

positive drug assocated experiences (eg euphoria, subjective high, pleasurable sensations)

Question 5

what are the two components of reward

Answer 5

liking: pleasurable, hedonic effects of the rewarding substance
wanting: craving, willingness to work for the reward

Question 6

is it generally accepted that dopamine is involved in the pleasurable effects of drugs of abuse

Answer 6

no, it is believed dopamine is not involved

Question 7

what do DA cells increase their firing to

Answer 7

unexpected rewards and conditioned cues signalling reward

Question 8

what do DA neurons shut off for

Answer 8

expected rewards that are then not received

Question 9

what do drug self administration studies show us

Answer 9

the abuse potential of that drug
rats learn that pressing a lever gives a dose of that drug
it uses fixed ration schedules so that a drug is administered after a fixed number of lever presses

Question 10

with a fixed ratio schedule, what is the typical shape of the curve and what happens at higher doses

Answer 10

shape is an inverted U
at higher doses the number of reinforcers can decline (can be due to satiation, aversive reactions, or disruptive side effects)

Question 11

what is progressive ratio in studying drug reinforcement in animals

Answer 11

schedule where the number of presses to get a drug infusion increases after each dose
this measures the breakpoint where the animal gives up on wanting the drug because its too much work to get it
this is a classic measure of the strength of drug reinforcement (how motivated animals are to obtain the drug)

Question 12

what does DA depletion in the NAc do

Answer 12

it attenuates or abolishes the initial learning to self administer many drugs

Question 13

what does a DA antagonist do in an animal that has already learnt to self administer

Answer 13

increase self administration of drugs like cocaine on low-cost fixed ratio schedules
this is thought to be because the animal is taking more drugs so that they can offset the DA receptor activation that’s been reduced

Question 14

what does DA antagonism do for self administration on progressive ratio schedules

Answer 14

reduces self administration
this is interpreted as reduced motivation for the drug

Question 15

conditioned place preference to measure conditioned drug reward

Answer 15

relies on a learned association between drug effect and environment
technically this assay doesn’t measure reinforcement because the animal gets frug no matter what it does
this is a measure of the attractiveness of drug associated environments: cues associated with the reinforcing properties of drug bias approach behaviour

Question 16

when can drugs establish a place preference

Answer 16

when given systematically or directly into the NAc and/or the VTA

Question 17

how can place preference for drugs be abolished

Answer 17

blockade of DA receptors

Question 18

how can conditioned preferences in humans be created and tested

Answer 18

ask them to conduct a memory task where they find the red ball and not the black one
when they find the red ball there is a pleasant tone, distinct patterned background, and a food reward
black ball = unpleasant sound, no reward, different patter
next do a preference test where they are shown different patterns (incl the one that was shown for the red ball) and ask which one they prefer
healthy humans preferred the pattern associated w the reward
patients w lower DA (had parkinsons) did not prefer the pattern associated with the reward

Question 19

how can the DA system be sensitized

Answer 19

with repeated exposure to all addictive drugs
repeated drug exposure can put the system into a hyperdopamine state which can lead to increased motivation to seek drugs in response to cues associated with the drugs