lec 7, drugs pt2 drug dependence

what mechanisms are in place so body can maintain homeostasis

negative feedback loops - metabolic tolerance and functional tolerance (change in receptor numbers, receptor sensitivity, intra-cellular cascades)

why does the body have homeostasis to respond to drugs

Homeostasis helps the body maintain stability - counters the effects of drugs.

what happens with tolerance mechanisms when stop taking drug

tolerance mechanisms are still there, the body may experience withdrawal symptoms as it attempts to regain balance. The tolerance mechanism is pushing the opposite way to the drug, so takes away from homeostasis in opposite direction. This leads to physical dependence

how is tolerance context dependent?

Classical conditioning means the body associates certain environments with the drug effects, leading to a built up tolerance in the same context.

how can being in unfamiliar environment cause overdose

In an unfamiliar environment, the body may not activate its tolerance mechanisms, leading to an unprepared state for the drug's effects. This can result in an overdose.

what is operant conditioning

stimulus triggers behaviour, leads to reward or consequence, which reinforces or discourages the behaviour

whjat did olds and milner find using intra cranial self stimulation in rats

they found a reinforcement system in the brain which, when active, increases behaviour

what are the main vbrain areas involved in self stimulation

nucleus accumbens and the ventral tegmental area (VTA). they are apart of the mesotelencephalic dopamine system

where in the brain is the mesotelencephalic located

system that connects the midbrain (mesencephalon) to the hindbrain (telencephalon)

what is the medial forebrain bundle

a bundle of axons that run from mesencephalon to telencephalon, using dopamine as their neurotransmitter.

what is dopamines involvement in reward

dopamine is released when reward is happening

this is correlational, not a causation. need to test whether dopamine is causally involved in reward-related behaviour.

How would you test whether dopamine release is causally involved in the rewarding effect?

Block the action of dopamine while stimulating

What did Stellar, Kelley + Corbett stimulate in rats

the medial forebrain bundle - releasing dopamine which meant rats were self stimulating

What did stellar, Kelley and Corbett do to the dopamine receptor blocker

They infused the dopamine receptor blocker (which is an antagonist) into the nucleus accumbens. When this is infused they wont learn to press the lever.

What do the findings of stellar Kelley and Corbett show

Only learn when stimulation, not stimulation and antagonist.

Dopamine released by stimulation is responsible for brain learning .

When is dopamine also released

When punished. Evidence to show dopamine not related to pleasure

What has dopamine been showed to be related to instead

Wanting and seeking

How is dopamine related to seeking

Gathering information and compulsion to repeatedly do something e.g. drug addicts taking drugs even when don’t enjoy.

What is psychological dependence

Drugs directly interact with brains reward system. Addict craves drugs even when disliking effects

What happens when infusing drugs directly into the nucleus accumbens (Cocaine is not going anywhere else other than NA)

Animals will learn to self administer

Cocaine having direct effect on mesotelencephalic dopamine system

What do psychologically addictive drugs do (such as cocaine and amphetamine)

They bypass all systems which assess if something is good or bad, they instead go straight to activating dopamine in nucleus accumbens, which gives you the compulsion to do it again.