[Distribution of acetylcholinesterase activity in the digestive system of the gastropod molluscs Littorina littorea and Achatina fulica].

With the use of the histochemical procedure for the demonstration of acetylcholinesterase (AchE) activity, the distribution cholinergic regulatory elements was studied in the esophagus, the pharynx, the stomach, the liver (the digestive gland) and the intestine in sea and terrestrial gastropod molluscs that differed in their general organization level, lifestyle, habitat and feeding type. In both molluscs, all the parts of the digestive tract contained the significant amount of intraepithelial AchE-positive cells of the open type, single subepithelial neurons and the nervous fibers localized among the muscle cells of the wall of the organs. The basal processes of the AchE-positive intraepithelial cells were shown to form the intraepithelial nerve plexus and to pass under the epithelium. The peculiarities and common principles in the distribution of the nervous elements detected, their possible function and the regulatory role in the digestion in gastropod molluscs and other animals are discussed.