Vasoactive intestinal contractor: Localization in the opossum esophagus and effects on motor functions

Abstract

Background/Aims: Vasoactive intestinal contractor (VIC), an endothelinlike peptide and a putative gastrointestinal hormone, contracts gastrointestinal smooth muscle. The aim was to study VIC in relation to esophageal function. Methods: Intramural nerves in opossum esophageal smooth muscle strips were stimulated in the presence of various concentrations of VIC and were stained for VIC immunoreactivity. Results: VIC caused an atropine-resistant increase in the amplitude of nerve-induced contractions of the circular muscle. VIC alone contracted longitudinal muscle, and this effect was nearly eliminated by 1 mmol/L atropine. VIC caused an atropine-resistant increase in the resting tone of the lower esophageal sphincter muscle, but it did not affect nerve-induced relaxation of that muscle. VIC-immunoreactive nerve fibers occurred in the longitudinal muscle layer, in the muscularis mucosae, and around the ducts of esophageal glands. A few such fibers were found in the circular muscle layer. Nerve fibers and cell bodies of the myenteric plexus showed VIC immunoreactivity. In the stomach, immunoreactive nerve fibers occurred in muscularis mucosae and circular muscle but not in longitudinal muscle. Conclusions: VIC is localized in neuronal elements of the opossum esophagus and excites contractions in esophageal smooth muscle.