Vasoactive intestinal contractor: localization in the opossum esophagus and effects on motor functions.
OBJECTIVE
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.
Department of Internal Medicine, College of Medicine, University of Iowa, Iowa City.
S
S
Fang
A
A
Ledlow
J A
JA
Murray
J
J
Christensen
J L
JL
Conklin
D000818:Animals; D001285:Atropine / Q000494:pharmacology; D004558:Electric Stimulation; D004947:Esophagus / Q000187:drug effects / Q000294:innervation / Q000378:metabolism / Q000502:physiology*; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism; D007150:Immunohistochemistry; D036341:Intercellular Signaling Peptides and Proteins; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D009197:Myenteric Plexus / Q000378:metabolism; D009412:Nerve Fibers / Q000378:metabolism; D009893:Opossums; D010455:Peptides / Q000378:metabolism / Q000502:physiology*; D013270:Stomach / Q000294:innervation
D036341:Intercellular Signaling Peptides and Proteins; D010455:Peptides; C059568:vasoactive intestinal constrictor; D001285:Atropine