The effects of diethyl ether, enflurane, and isoflurane at the neuromuscular junction

The actions of diethyl ether, enflurane, and isoflurane at the neuromuscular junction were examined in isolated guinea pig lumbrical muscles. These anesthetics depressed the ability of carbachol to depolarize the endplate region; this depression of depolarization did not show competitive kinetics. None of the anesthetics altered the affinity of the acetylcholine receptor for d-tubocurarine, i.e., the dissociation constant of d-tubocurarine was unchanged. Since diethyl ether, enflurane, and isoflurane produced no observable alteration of the receptor, the antagonism of the drug-induced depolarization of the neuromuscular junction appears to be exerted at a stage subsequent to reaction with the receptor. (Key words: Anesthetics, volatile, diethyl ethers; Anesthetics, volatile, euflurane; Anesthetics, volatile, isoflurane; Neuromuscular relaxants, d-tubocurarine; Neuromuscular junction.).