topic 3 - reward and drug addiction Flashcards
(19 cards)
define drugs
chemical substance which interacts with biochem of the body
what are psycho-active drugs?
chemicals which influence the way we feel or act. usually interact with the nervous system and/or endocrine system. mostly act on synapses
what are the effect of agonist and antagonist drugs at the synapse level?
- effect post-synaptic cell
- agonist = mimics action of the neurotransmitter
- antagonist = blocks action of the neurotransmitter
what are the effect of agonist and antagonist drugs at the receptor level?
- effects receptors
- agonist = mimics action of neurotransmitter
- antagonist = blocks action of neurotransmitter
how can a drug be both an agonist and antagonist?
- some drugs can be agonist on the receptor binding like a neurotransmitter. this then stops more neurotransmitter being released at the presynaptic terminal meaning overall at the synapse the drug is antagonist
- opposite, drugs can be antagonist at receptors by binding and stopping neurotransmitters binding. but more neurotransmitter is still released so at synapse level is an agonist
routes of intake fore pharmakinetics
- digestive tract
- respiratory tract
- through skin
- mucous membrane
- intravenous injections - directly into blood
- intramuscular injection - into muscles
- subcutaneous injection - under the skin
which method of intake of pharmakinetics is fastest and slowest
fastest = intravenous
slowest = digestive tract
describe the distribution of pharmokinetics
- water-soluble molecules can be directly dissolved in the blood, but do not pass through cell membranes
- lipid-soluble molecules need carriers to transport them through the blood but can pass directly through cell membranes due to lipid bilayer
pharmakinetics : elimination
- ## all drugs are eventually eliminated from the body by chemical break down or by excretion
drug tolerance
- body maintaining homeostasis
- mechanisms:
–> metabolic tolerance
–> functional tolerance (change in receptor numbers, change in receptor sensitivity, change in intra-cellular cascades)
consequence of tolerance
- leads to withdrawal effects
- tolerance mechanism doesn’t just disappear once drug is no longer taken
- and tolerance takes body away from homeostasis
- opposite effects of drug
is tolerance context dependent?
- yes
- can classically condition body to have higher tolerance to drug when in certain context
- well known in heroine addicts
- overdosing is easier in novel surroundings
- withdrawal symptoms also occur in familiar settings
psychological dependence - operant conditioning
- reinforcing behaviour maintaining drug taking
- evolutionarily good
what is intracranial self-stimulation
- electrode in rat brain
- measure activation
- skinners box
- map out stimulation rewarding behaviour activation in brain
role of dopamine in reward behaviour
- prove causation instead of just correlation
- stimulated medial forebrain bundle releasing dopamine getting rats to self stimulate
- infused the dopamine receptor blocker an antagonist into the nucleus accumbens animals wont learn to press the lever
- when only do the stimulation then they will learn
- showing that its the dopamine causing the learning response
dopamine just for reward/pleasure?
- no
- also released for punishing stimuli as well
- overtrained rats do not release dopamine upon reward
- dopamine blockers make rats work less hard for food, but still enjoy
- endogeonous opiods invloved in pleasure responce
dopamine about seeking or wanting
- dopamine is about compulsion rather than wanting something
- drug addicts will experience a compulsion for drug even tho they dont enjoy taking it anymore
- rats in a novel environment release dopamine even tho theres nothing rewarding about it
- male rat put in novel cage, after home cage (baseline), female introduced but male cant reach dopamine increases, then they can be together and then taken away
