The Effects of Vagal Nerve Stimulation on Endoluminal Release of Serotonin and Substance P into the Feline Small Intestine

Abstract

Endoluminal release of serotonin (5-HT), substance P (SP), and motilin was quantitated after thoracic vagal nerve stimulation in the cat. In duodenum and jejunum, simultaneous release of these compounds was observed. In contrast, vagal stimulation did not augment the rate of luminal secretion of either 5-HT or SP in the distal ileum. Immunohistochemical studies demonstrated 5-HT in both enterochromaffin (EC) cells and nerves throughout the small bowel. However, we were unable to visualize any SP-containing EC cells in the cat, which suggests that the source of luminal SP in this species must be intramural nerves.

Enterochromaffin cells of the digestive system: cellular source of guanylin, a guanylate cyclase-activating peptide.

“…However, increasing evidence exists also for an endoluminal release of EC-cell secretory constituents (36)(37)(38); such a luminocrine secretory pathway is attributed to open type EC cells that reach the gut lumen by apical cell processes (30,36). Indeed, release of serotonin into the gut lumen has clearly been demonstrated (38)(39)(40). Since guanylin is present in EC-cell secretory granules where serotonin is also localized, EC cells predictably release guanylin not only into the circulation but also into the gut lumen.…”

“…At least one function of EC cells is apparently related to local regulation of water and electrolyte secretion in the gastrointestinal epithelium through a luminocrine secretory pathway. The luminocrine secretory activity of EC cells is obviously under vagal control (39,40), and interpreted retrospectively, diarrhea observed after stimulation of EC cells (41,42) may be attributed to guanylin secreted by these cells into the gut lumen. In this respect, future studies should focus on the regulation of guanylin biosynthesis in EC cells and in tumors derived from them (e.g., carcinoids) of which one predominant and common effect is diarrhea.…”

Maintenance of Serotonin in the Intestinal Mucosa and Ganglia of Mice that Lack the High-Affinity Serotonin Transporter: Abnormal Intestinal Motility and the Expression of Cation Transporters

“…Platelets primarily obtain 5-HT by taking it up within the gut. EC cells constitutively secrete 5-HT (Toh, 1954;Schwörer et al, 1987b) and release more when stimulated to do so (Ahlman and Dählstrom, 1983;Grønstad et al, 1985;Schwörer et al, 1987a;Racké et al, 1988;Wingren et al, 1988;Grider et al, 1996). EC cell 5-HT can overflow to the intestinal lumen (Nilsson et al, 1987;Wingren et al, 1988), can be inactivated by uptake and metabolism within the mucosa (Gershon and Ross, 1966a;Pan and Gershon, 2000), or can reach the portal circulation (Toh, 1954;Schwörer et al, 1987b).…”

Peptidergic sensory neurons in the control of vascular functions: Mechanisms and significance in the cutaneous and splanchnic vascular beds

“…A role of peptidergic afferent neurons in wound healing can also be envisaged from the ability of SP, NKA and CGRP to stimulate the proliferation of endothelial cells (Haegerstrand et al 1990;Ziche et al 1990), arterial smooth muscle cells (J. Nilsson et al 1985Nilsson et al , 1986Payan 1985) and skin fibroblasts (J. Nilsson et al 1985).…”