Galanin and Vasoactive Intestinal Polypeptide: Coexistence and Corelease from the Vascularly Perfused Pig Ileum during Distension and Chemical Stimulation of the Mucosa

Abstract

By immunohistochemistry and double staining technique, almost complete coexistence of galanin-like immunoreactivity (GAL-LI) and vasoactive intestinal polypeptide-like immunoreactivity (VIP-LI) was demonstrated in submucosal ganglionic cells and mucosal nerve fibers of the porcine ileum. The release of the two neuropeptides was studied in isolated, vascularly perfused pig ileum. Distension (increasing intraluminal pressure by 10 mm Hg) and intraluminal instillation of homologous gallbladder bile, amino acids, 0.1 M HCl, hypertonic NaCl (3,400 mosm x kg-1) and hypertonic glucose (1,100 mosm x kg-1) all increased the release of GAL-LI and VIP-LI into the venous effluent in parallel. Being the most potent stimulus, bile increased the output of GAL-LI from 0.74 +/- 0.12 to 2.44 +/- 0.81 pmol/min (mean +/- SE, p = 0.018) and the output of VIP-LI from 3.29 +/- 0.19 to 12.68 +/- 4.01 pmol/min (p less than 0.001), respectively. In conclusion, the coexistence and parallel release of GAL and VIP suggest that GAL/VIP neurons may be involved in intramural secretory and motor reflexes.