A comparison of acetylcholine and stable depolarizing agents

Abstract

The method of brief ionophoretic application was used to compare the time course of action of acetylcholine and of stable depolarizing substances. The drugs were discharged from twin micropipettes, allowing a quick comparison of two substances, applied from virtually the same point source. With pulse application at close range, the time course of an acetylcholine potential is faster than those produced by other drugs. Comparing half-times of decay, if that of the acetylcholine potential is taken as unity, carbaminoylcholine is slower by a factor of about 2, nicotine and succinylcholine by 2 to 3, and decamethonium by approximately 10. After treating the muscle with prostigmine, the average difference in time course between acetylcholine and carbachol effects becomes insignificant. Different processes are discussed whose kinetics influence the shape of the observed drug potentials.