lecture 15 LOs Flashcards
what system do all drugs of abuse w high addictive potential activate either directly or indirectly
mesolimbic dopamine system
drugs of abuse activate the brains ____, but can do so to a much ____ degree
natural reward pathways, greater
what does a drug being a positive reinforcer mean
consuming the drug strengthens whatever preceding behaviour was performed
what does drug reward refer to
positive drug assocated experiences (eg euphoria, subjective high, pleasurable sensations)
what are the two components of reward
liking: pleasurable, hedonic effects of the rewarding substance
wanting: craving, willingness to work for the reward
is it generally accepted that dopamine is involved in the pleasurable effects of drugs of abuse
no, it is believed dopamine is not involved
what do DA cells increase their firing to
unexpected rewards and conditioned cues signalling reward
what do DA neurons shut off for
expected rewards that are then not received
what do drug self administration studies show us
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
with a fixed ratio schedule, what is the typical shape of the curve and what happens at higher doses
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)
what is progressive ratio in studying drug reinforcement in animals
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)
what does DA depletion in the NAc do
it attenuates or abolishes the initial learning to self administer many drugs
what does a DA antagonist do in an animal that has already learnt to self administer
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
what does DA antagonism do for self administration on progressive ratio schedules
reduces self administration
this is interpreted as reduced motivation for the drug
conditioned place preference to measure conditioned drug reward
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
when can drugs establish a place preference
when given systematically or directly into the NAc and/or the VTA
how can place preference for drugs be abolished
blockade of DA receptors
how can conditioned preferences in humans be created and tested
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
how can the DA system be sensitized
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
