The neuromuscular blocking action of suxamethonium on the rat diaphragm.

Experiments are described using the rat isolated phrenic nerve diaphragm preparation, in which suxamethonium produced a neuromuscular block consisting of an initial phase of fairly sharp onset followed by a prolonged phase, which first remained at a steady level and then slowly decreased in intensity over several hours. Suxamethonium block is antagonised by potassium and intensified by tubocurarine in both phases. It would therefore appear that the depolarising action of suxamethonium is complicated by some measure of competitive inhibition in the isolated nerve-muscle preparation as in the intact animal.