Session 10: The ANS/Pharmacokinetics

Question 1

Compare the pathways of cholinergic/adrenergic receptors for synthesis, storage, release and termination

Answer 1

Synth: Acetyl CoA + Choline catalysed by choline acetyltransferase/see diagram

Storage: both stored in vesicles, in NAdr this is due to the vesicular transporter exploiting a H⁺-ATPase-generated cytoplasm:vesicle H⁺-gradient

Release: both by Ca²⁺ mediated exocytosis: depol. of nerve terminal membrane-> Ca²⁺ entry -> fusion of vesicles w/ presynaptic PM

Termination: cholinesterase degrades ACh-> choline and acetate, inc. activity at fast nicotinic chol. synapses, choine transporter in syn. terminal recaptures most choline

• > NAdr: Uptake 1: rapidly removes NAdr from cleft, dec. local conc. and terminating its actions, NEpin. Transporter converts it to Adr.
• Uptake 2: widespread, low aff., taken up by non neuronal cells in vicinity -> recycled or metabolised (by Monoamine Oxidase/MAO)