Biphasic relaxation of the opossum lower esophageal sphincter: Roles of NO·, VIP, and CGRP

Aliye Uc, S. T. Oh, Joseph A. Murray, Eugene Clark, Jeffrey L. Conklin

Research output: Contribution to journalArticlepeer-review

28 Scopus citations


Vasoactive intestinal polypeptide (VIP) and nitric oxide (NO·) are thought to mediate lower esophageal sphincter (LES) relaxation. Transverse muscle strips from the opossum LES were used to test this hypothesis. Electrical field stimulation (EFS) produced a biphasic LES relaxation: a rapid component during the stimulus was more prominent at lower stimulus frequencies, and a sustained component was more prominent at higher frequencies. N(ω)-nitro-L-arginine and hemoglobin inhibited the rapid component but affected the sustained component less. Exogenous VIP decreased LES tone. A number of purported VIP antagonists blocked neither VIP-induced nor EFS-induced relaxation of the LES. The calcitonin gene-related peptide (CGRP) antagonist CGRP-(8 - 37) did not alter EFS-induced LES relaxation. EFS-induced relaxation of opossum LES muscle is biphasic, and the initial, rapid component of the relaxation is mediated primarily by NO·. The mediator of the sustained component was not identified.

Original languageEnglish (US)
Pages (from-to)G548-G554
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Issue number3 40-3
StatePublished - Sep 1 1999


  • Calcitonin gene-related peptide
  • Enteric nervous system
  • Gastrointestinal motility
  • Nitric oxide
  • Smooth muscle
  • Vasoactive intestinal polypeptide

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)


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