voicesinmyhead

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Mariana Trench
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Is succinyl CHoline a competitive or a non competitive blocker of the Nicotinic Ach receptor?

It says its competitive at some places, but also non competitive (since block phase 1 not reversed by excess Ach) at others.

Kindly help?
 
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I dont think competitive/ non competitive applies to Suc/chol since it's not an antagonist.. It just cause the NMJ to fire so much that you get paralysis of muscle due to desensitization , thats why its early phase is irreversible , the Ach Receptor is 100% desensitized
 

Transposony

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It does indeed has a dual mechanism.
Initially, Succinylcholine is a depolarizing, noncompetitive nicotinic agonist.
Succinylcholine is basically two molecules of Acetylcholine bound together which depolarizes the membrane by opening channels in the same manner as ACh.
This depolarization initially results in a brief period of repetitive muscle excitation (fasciculations) followed by NMJ block and flaccid paralysis (Phase I) as desensitization occurs due to Na channel blockade.
Since it is Ach like the NMJ block will not be reversed by AchE inhibitors. In fact AchE inhibitors potentiates Phase I.
This is followed by a non-depolarizing, phase II block which can be antagonized by AChE inhibitors.
 
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