the mechanism of acetylcholinesterase inhibition?
The simple and widely accepted mechanism of
acetyl-cholinesterase inhibition is the law of mass action. Large amounts of
acetylcholine at the neuromuscular junction secondary to inhibition of
acetylcholinesterase increase the interactions between acetylcholine and its
postjunctional receptor. Excess acetylcholine effectively competes with
nondepolarizing muscle relaxants for nicotinic receptor binding sites on the
postjunctional membrane. Additionally, quaternary amines appear to exert a direct
stimulatory action on skeletal muscle. Denervated muscle or muscle whose nerve
terminals lack acetylcholine con-tract after exposure to quaternary
acetylcholinesterase inhibitors, implying a direct action by these agents.
Also, acetylcholinesterase inhibitors can convert a single action potential in
a motor nerve into a pattern of repetitive firing. This repetitive firing may
spread retrograde up the axon, causing other nerves in the same motor unit to
fire. This results in increased muscular contraction.