sympathetic nervous system Flashcards
methyldopa: identify the actions of the false transmitter methyldopa and identify its clinical uses and side effects
what is methydopa used as
antihypertensive agent
what is methyldopa
false transmitter
what reactions does methydopa undergo and what is the fale transmitter product
taken up by noradrenergic neurones, decarboxylated and hydroxylated to form a-methyl-noradrenaline, which is less active at a1/B1 adrenoceptors
how does a-methyl-noradrenaline displace noradrenaline from synaptic vesicles
reuptaken by uptake-1 into presynaptic neurone, but not deaminated within neurone by MAO, so tends to accumulate in larger quantities than noradrenaline -> a-methyl-noradrenaline concentration gradient is reduced, so uptake slower and remains in synaptic cleft for longer -> binds to a2 receptors so further negative feedback and inhibition of noradrenaline release
where is methydopa especially anti-hypertensive
renal (if due to kidney disease), CNS (if due to cerebrovascular disease; stimulates vasopressor centre in brain stem to inhibit sympathetic outflow)
3 adverse effects of methyldopa
dry mouth (prevents production of thick, viscous secretions), orthostatic hypotension (can be limiting), male sexual dysfunction
