Actions of triethylcholine on neuromuscular transmission

摘要

During an investigation of the anticholinesterase activity of a series of bisphenacyl derivatives, Schueler and his colleagues in New Orleans had found, in the mid 1950s, that one of them (later called hemicholinium No 3, HC-3) was virtually devoid of anticholinesterase activity but exhibited an unusual form of delayed paralysing activity in mice. The molecule contained two choline-like moieties and it underwent hemiacetal formation in solution; hence the name "hemicholinium" coined by Schueler. Later work, much of which was reviewed by Bowman & Marshall (1972) and Macintosh & Collier (1976), showed that HC-3 acts by competing with choline for transport into cholinergic nerve endings. It thereby deprives the nerve endings of the choline needed for acetylcholine synthesis, and so an important component of its blocking action is pre-junctional in origin. Characteristically its blocking action is slow in onset and dependent on a high frequency of nerve impulses; its inhibitory action on choline transport is overcome by an excess of choline. Although it enters the axoplasm, HC-3 cannot be released by nerve impulses (Collier, 1973).