L12 - socially used and abused drugs Flashcards
how do social drugs evoke pleasure
activate dopaminergic reward pathways in brain
where is the dopaminergic reward pathway
runs from the vetral tegmental area (VTA) to nucleus accumbens (NA)
what is the direct activation of the reward pathway
VTA sends direct signals to Nucleus accumbens causing dopamine release
drugs can cause these signals to activate
what is the indirect activation of the reward pathway
the reward pathway is under inhibition control
so drugs that inhibit this inhibition will activate the pathway
what drugs can cause direct activation of the dopaminergic reward pathway
nicotine and ecstasy
what drugs can cause indirect activation of the dopaminergic reward pathway
cannabis
what is found in cigarettes
nicotine
arsenic
methanol
DDT
effect of nicotine in the periphery
agonist at NAChRs
- excite ANS ganglia - cause A release from medulla
- slowed HR
- vasoconstriction
- increased BP
effect of nicotine in CNS
release of many transmitters eg
- dopamine
- ACh
- serotonin
how much more sensitive are NAChR’s in brain than NAChR’s in muscle?
50x more sensitive in CNS
how are cigarettes toxic?
- produce CO that displaces O from Hb
- nicotine is vasoconstrictor and causes platelet aggregation
- contains tar and irritants (carcinogenic)
what is the effect of nicotine on expression of NAChR’s?
increased exposure to nicotine causes increased expression of NAChR’s
where does heroin come from
opium poppy - synthesised from morphine - twice as potent
what happens to heroin in the body
crosses BBB and is converted into morphine
what receptors does heroin bind to and where are they located
opiate receptors in reward/pleasure areas (VTA and NA)
effects of heroin
euphoria
addiction
describe the acute toxicity of heroin
mild respiratory depression
describe the chronic toxicity of heroin
severe respiratory depression
extreme sedation (confusion, anxiety)
respiratory failure
effects of ecstasy
psychoactive stimulant
empathogenic
euphoria, arousal, endurance
source of ecstasy?
synthetically made
how does ecstasy produce its effect?
E displaces serotonin from vesicles
serotonin leaks out into cleft
E also blocks Serotonin reuptake pump
secondary rise in NA and A
describe acute toxicity of ecstasy
- hyperthermia (high temp) due to increased NA and metabolism and inability to regulate it
- hyponatraemia (reduced blood NA+) due to sweat and drinking too much
- exhaustion, irritability, low mood
what is hyponatraemia
low blood Na+
describe chronic toxicity of ecstasy
depression/anxiety
memory impairment
why is it difficult to asses drug toxicity
- people lie about drugs taken / how much
2. purity of drugs varies
how was rationale scale of drug safety made
a graph of dependence on drug and toxicity (physical harm)
