Biochemical Evidence for the Neural Function of Acetylcholine

Abstract

The author discusses evidence for biological synthesis of acetylcholine; the discovery, measurement, and properties of choline acetylase; comparative distribution of choline acetylase in organisms lacking a nervous system (Lactobacillus plantarum, Paramecium, Trypanosoma rhodesiense, Plasmodium gallinaceum), in non-nervous tissue of Mytilus edulis, and in non-nervous tissue (placenta, red blood cells, cardiac muscle, intestinal layers, spleen) of man. Its concentrations in various nervous tissues of man, other mammals, and some birds are given; also its time of first appearance in the cerebrum of the rabbit and the guinea pig. The evidence about the distribution of acetylcholine and the enzymes which metabolize it in the nervous system is compatible with the theory of the chemical transmission of nervous impulses and supports the view that the theory may apply equally well to some, but not to all, central nerve pathways. The wider distribution of the enzymes cannot be accounted for as yet by any theory of acetylcholine action, but this need not affect the arguments about its neural function. What is now required is more precise information about their distribution within the neurons in which acetylcholine metabolism has a proved function. Present knowledge suggests that it is the structural disposition of acetylcholine which determines its functional specificity in nervous tissue.