Surgeons use the drug succinylcholine, which is an acetylcholine analog, as a mu
ID: 20365 • Letter: S
Question
Surgeons use the drug succinylcholine, which is an acetylcholine analog, as a muscle relaxant. Care must be taken because some individuals recover abnormally slowly from this paralysis, with life-threatening consequences. These individuals are deficient in an enzyme called pseudochlinesterase, which is normally present in the blood, where it slowly inactivates succinylcholine by hydrolysis to succinate and choline.If succinylcholine is an analog of acetylcholine, why do you think it causes muscles to relax, and not to contract as acetylcholine does?
Explanation / Answer
Succinylcholine inhibits the action of acetylcholine at the neuromuscular junction, acting non-competitively on muscle-type nicotinic receptors. Without the pseudo-cholinesterase this non-competitive inhibition will not be overcome by the hydrolysis you described, and muscles stay catatonic. So SAch does not act on mAchR, it inhibits the receptor, preventing ACh from acting upon it and inducing muscle response.
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