Recovery of acetylcholinesterase at intact neuromuscular junctions after in vivo inactivation with di-isopropylfluorophosphate.

Recovery of acetylcholinesterase (AChE) at endplates of mouse sternomastoid muscle was studied after inactivation with di-isopropylfluorophosphate in vivo. A short incubation with alpha-bungarotoxin was used to prevent muscle necrosis which usually occurs after esterase inactivation. Under these conditions there was no delay in AChE recovery, unlike what we had previously seen in necrotic muscle. However, even in non-necrotic muscle, the overall recovery of AChE at the postjunctional membrane was very slow, with a half-life of about 20 days. The fact that, at adult neuromuscular junctions, both esterases and receptors turn over about 10 times slower than they do in embryonic muscle suggests a similar regulation of these two molecules by the nerve.