Distribution of peptide- and catecholamine-containing neurons in the gastro-intestinal tract of rat and guinea-pig: immunohistochemical studies with antisera to substance P, vasoactive intestinal polypeptide, enkephalins, somatostatin, gastrin/cholecystokinin, neurotensin and dopamine beta-hydroxylase.

Publisher Summary This chapter discusses the innervation of the gastrointestinal tract. It examines the structures involved in nervous control of the activities of the gastrointestinal tract. They can be classified as (1) nerve pathways reaching the gastrointestinal tract, including afferent and efferent pathways, (2) ganglia and plexuses located within the wall of the stomach and the intestine, and (3) terminal parts of nerve fibers making contact with the effectors (muscular and glandular) or forming sensory endings. The effectors include secretory cells and smooth-muscle cells of the intramural blood vessels and of the muscle layers proper. The presence of highly developed intramural plexuses is a characteristic feature of the gastrointestinal tract. It is probably related to the complexity of functions of the vertebrate gut, notably regulated propulsive activity. The efferent pathways leading to the gastrointestinal tract can be divided into three major groups: (1) the vagus nerves, (2) the splanchnic nerves, with the abdominal plexus and its perivascular nerves reaching the stomach and intestine, and (3) the pelvic plexus and its nerves.

Innervation of the gastrointestinal tract

Substance P immunoreactivity has been demonstrated in the mouse gut in two distinctly different locations; in the myenteric plexus of the proximal colon as well as in endocrine-like cells of the duodenal and colonic mucosa.

Localization of substance P-like immunoreactivity in mouse gut.

The properties of a vasodepressor substance extracted from brain and intestine and originally called preparation P were first described by von Euler and Gaddum in 1931. Fifty years later, it is certain that substance P must play an important role in nervous system function, yet it is surprisingly difficult to cite a single physiologically relevant action of substance P, supposedly the doyen of the common peptides (Pearse, 1978). In contrast, the physiological role of many other neuropeptides and releasing hormones that have been discovered more recently is now well established.

Substance P in the Nervous System

Immunoreactive Substance P is localized in the intramural neural plexuses of mammalian intestine, and in endocrine cells in the intestinal mucosa which have now been identified as enterochromaffin (EC). The presence of a neurotransmitter peptide in these cells favours the hypothesis of their neuroectodermal origin.

Enterochromaffin cells as the endocrine source of gastrointestinal Substance P

The AA present a study of 3 cases of Hirschsprung's disease performed under electron microscopy and whose data seen to suggest that substance P, which is always found in larger amounts in the ganglionic portion of the colon (than in the aganglionic one), may be related with the granular vesicles of Auerbach's plexus.

L. Bogliolo

Papers

An electron microscope study of the Auerbach's plexus and determination of substance P of the colon in Hirschsprung's disease.