Muscarinic Receptors on Neurones of the Submucous Plexus

Abstract

The functions of the gastrointestinal epithelium are controlled by transmitters released from nerves. These nerves are of three main classes, corresponding to Langley’s (1921) divisions of the autonomic nervous system. First, sympathetic fibers reach the mucosa along the course of the blood vessels, passing directly through the enteric plexuses; however, a large number of sympathetic fibers end by making synaptic contacts with nerve cells of the submucous plexus and do not directly reach the mucosa (Costa and Furness 1984). Second, cholinergic nerves of the postganglionic part of the parasympathetic outflow innervate the mucosa. The cell bodies of these neurones constitute an unknown fraction of the neurones of the submucous plexus. Third, neurones intrinsic to the enteric nervous system, having their cell bodies in the submucous plexus, provide a dense projection to the mucosa. These cells are identified by their contents of cholecystokinin (CCK), neuropeptide Y (NPY), and the synthesizing enzyme for acetylcholine (ACh), choline acetyltransferase (ChAT) (for review, see Furness et al. 1984). Although the relative roles of the various types of innervation are not fully understood, it is well established that all three sets of nerves can under various circumstances have significant effects on secretory and absorptive activity (Gaginella and O’Dorisio 1979; Cooke et al. 1983; Tapper 1983).

The original work described here was supported by AM 32979