Socially used drugs

social drugs

a pharmacologically-heterogeneous group of drugs taken by choice that cause hedonic effects

how do social drugs evoke pleasure?

they activate the mesolimbic pathway - a dopaminergic reward pathway running from the ventral tegmental area (VTA) to the nucleus accumbens

direct activation of mesolimbic pathway

increased firing of VTA neurones to increase dopamine release in NA

indirect inhibition of mesolimbic pathway

decreased firing of GABAergic neurons that usually inhibit dopamine release

cigarette smoking source and active drug

nicotiana tabacum plant, nicotine

cigarette smoking effect

psyohoactive stimulant and relaxant
causes euphoria, increased alertness and concentration, relaxation

pharmacology of nicotine

nACh receptor agonist, leading to influx of cations and membrane depolarisation; excites autonomic ganglia in periphery leading to adrenaline release

toxicity of cigarette smoking (3)

carbon monoxide: displaces O2 from haemoglobin to form carboxyhaemoglobin, increases incidence of ischaemic heart disease
nicotine: vasoconstrictor, increases platelet aggregation
tar and irritants: increases incidence of lung cancer

source of cannabis and active component

cannabis sativa plant
marijuana = dried leaves and flowers, hashish = flower resin
delta-9-tetrahydrocannabinols (THC)

cannabis effect

dose-related - can be stimulant, depressant or hallucinogenic

pharmacology of cannabis

TCH activate endogenous CB1 and CB2 GPCRs, leads to inhibition of Ca2+ channel opening, decreased release of neurotransmitter

acute toxicity of cannabis

vasodilation (bloodshot eyes), drowsiness and confusion (due to decreased ACh)

chronic toxicity of cannabis

smoking related cancer, memory impairment, psychosis, reduced testosterone secretion, reduced immune response

ecstasy (MDMA) effect

psychoactive stimulant, empathogenic

MDMA source

synthetically made

pharmacology of ecstasy

E replaces 5-HT from vesicles in the serotonergic nerve ending, it also blocks the 5-HT reuptake pump, prolonging 5-HT action, leading to increased NA and dopamine release

symptoms of acute toxicity of ecstasy

hyperthermia, due to increased NA leading to increased metabolism
hyponatraemia: reduced blood Na+, due to perspiration

chronic toxicity of ecstasy

selective damage to 5-HT terminals
some reports of depression, anxiety and memory impairment