Factors Affecting Acetylcholine Found in Excised Rat Brain

Abstract

The amt. of acetylcholine (ACh) found in whole rat brain does not change rapidly after excision; in cortex it falls with time. Less ACh is found in the brains of small than of large animals. Freezing in liquid air causes a considerable loss of ACh. This does not occur with brains from eserinized animals. The ACh content of the brains of eserinized animals is elevated. Virtually all the ACh in brain is in the bound form. Acid, mechanical disturbance, freezing, hypotonic suspension medium and high K concns. accelerate liberation from the bound form. A very low concn. of free ACh may be maintained in brain in the absence of anticholinesterase. The bound ACh in brain slices increases considerably on incubation aerobically in the presence of glucose whether anticholinesterase is present or not. This increase is less marked in the presence of a high K concn. especially in the absence of anticholinesterase. Direct evidence is presented that the release of ACh from the bound form is reversible.