CB L2 - Drug addiction 2 Flashcards
(23 cards)
What receptor is thought to be responsible for conscious perception of euphoria?
D2 - eventually projects to the prefrontal cortex
How do we use PET scanning used to look at DA conc
infuses radio ligand for DA receptors.
If something happens to cause release of DA competing with this there is less radio ligand binding
If there is fewer receptors also less binding
What does PET scanning show on admin of methylphenidate?
DA response to methylphenidate is less in normal than cocaine abusers.
Are addicts born with less D2 receptors of is this a response to drug abuse?
Study gave non-addicts methyl phenidate and PET scanned:
Some people didn’t enjoy (heart racing), these people had more D2 recptor.
People who enjoyed it had fewer D2 receptors
Are addicts born with less D2 receptors of is this a response to drug abuse?
Study gave non-addicts methyl phenidate and PET scanned:
Some people didn’t enjoy (heart racing), these people had more D2 recptor.
People who enjoyed it had fewer D2 receptors
So how could number of receptors be a risk factors to becoming an addict?
Fewer D2 receptors in addicts and non-drug abbuser who enjoyed the methyl phenidate expereince
Cocaine self-administration for rats with high vs low D2 receptors showed…
ref?
Rats with lower D2 density took more cocaine than those with lower D2 density
Dalley, (2007)
Chronic cocaine admin in mokeys over 1 year showed…
ref
limitations?
decline in D2 expression.
Nader, 2006
might only apply to pyschostimulants as other drugs havent been investigated
Over all the D2 concentration studies indicate:
People with fewer D2 receptors might have a greater drive to take rewarding drugs (might like them more)
How could a SNP affect D2 expression? (in theory)
reduced expression of D2 receptor.
But this is also affected by you environment
How could a SNP affect D2 expression? (in theory)
reduced expression of D2 receptor.
But this is also affected by you environment
Put an animal in an unrewarding cage (no toys/isolation/boring food) - what happens?
ref?
Decreases D2 levels and increases cocaine self-administration.
Nader 2006
Mokeys live in packs - dominant levels of D2 are higher/lower?
higher - less likely to take cocaine.
So maybe your environment causes changes to expression levels?
Intrudedr test is
putting monkeys in a cage, introduce an intruder and monkeys throw poo at it, only works if intruder is submissive, otherwise it throws poo.
Dominant monkeys hardly took cocaine. For the submissive monkeys this is really unpleasant so took a fuck tonne.
Dominant already had their reward and felt good?
So the D2 receptor levels affefted by the environment suggests the best way to treat addicts is…
by changing their environment!
Outline of Low D2 receptor levels whole theory:
may be the case for other drugs but atm only looked at psychostimulants
Not much reward in your life (environmental factors) and genetic factors lead to low D2 levels.
Low endogenous reward ‘tone’
Enhanced ‘liking’ of drugs of abuse
Enhanced drug intake
Outline of Low D2 receptor levels whole theory:
may be the case for other drugs but atm only looked at psychostimulants
Not much reward in your life (environmental factors) and genetic factors lead to low D2 levels.
Low endogenous reward ‘tone’
Enhanced ‘liking’ of drugs of abuse
Enhanced drug intake
So enhancing reward might decrease use of drugs of abuse…. economical?
Pharmacological treatments suggested? (2)
yes - costs loads to treat addicts
Bupropion - (NA/DA reuptake inhibitor)
Bromocriptine (partial D2 agonist)
maybe mrore effective in people with certain D2 SNP?
Problems with the D2 receptors hypothesis 3
- There are D2 receptors everywhere so we are assuming the ones in the NAcc are most important.
- Lots of other brain regions involved such as memory
- Taking drug is no longer for euphoria - emotion and copulsion elements.
Memory formation is thought to occur through
synaptic plasticity.
Psychological dependence (addiciton, craving) must have a ……. component
learned
How is DA release a predictor of reward - human example
ref
DA gets released as you anticipate taking the the drug.
If you show addicts films of people taking the drug they release DA (doesn’t happen in non-addicts)
volkow, 2006, 2011
How is DA release a predictor of reward - animal example
ref
DA gets released when the lever appears in animal models (higher spike than actual reward from drugs).
During extinction this still occurs, but animal doesn’t get cocaine. Over time DA release wains,
