Importance of Calcium for Acetylcholine-evoked Salivary Secretion

Abstract

ONE of the functions of the chemical transmitter acetylcholine is to evoke secretion. How it does this is unknown; but recent evidence¹ indicates that, at one of its sites of action, the adrenal medulla, acetylcholine stimulates secretion through some calcium -dependent process. Thus, the stimulant effect of acetylcholine on catecholamine release was found to vary with the extracellular calcium concentration over a wide range, and calcium itself in certain circumstances proved an adequate stimulus for secretion. These observations considered along with the known ability of acetylcholine to increase membrane permeability at various sites led to the suggestion that acetylcholine evokes catecholamine secretion by promoting the influx of calcium into the chromaffin cells¹. This idea gains support from experiments showing that acetylcholine increases the uptake of calcium-45 by the adrenal medulla².