Substance P: Mechanism of action and receptor distribution at the feline ileocecal sphincter region

R. D. Rothstein, E. Johnson, A. Ouyang

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The purpose of this study was to determine the mechanism of action of substance P at the distal ielum, ileocecal sphincter (ICS), and proximal colon in the cat and to determine the localization of substance P receptors at these sites by autoradiography. Intraluminal pressures and myoelectric activity were recorded at the feline distal ileum, ICS, and colon. Substance P caused a tonic and phasic spike-dependent contractile response at all three sites. The antagonists propranolol, phentolamine, and naloxone did not affect the contractile response to substance P at the ileum, ICS, or colon. The ganglionic blocker trimethaphan camsylate potentiated the response to substance P at all three sites, P < 0.05. Both atropine and tetrodotoxin reduced the response of substance P at the ileal site. At the ICS, atropine or tetrodotoxin reduced, but did not obliterate, the effect of substance P. Neither atropine nor tetrodotoxin reduced substance P-induced colonic contractions. By use of autoradiography, specific binding for substance P was determined to be present at all three sites with the greatest concentration of substance P receptors in the circular muscle layer. In conclusion, these studies suggest multiple sites of action of substance P. At the ileum, substance P causes contraction via a cholinergic pathway. At the ICS, substance P has an excitatory action through a cholinergic pathway and also at smooth muscle receptors. In the proximal colon, the excitatory action of substance P is via smooth muscle receptors. An inhibitory ganglionic pathway also exists at all three sites. Substance P receptors exist predominantly in the circular muscle region of the ileum, ICS, and the proximal colon.

Original languageEnglish (US)
Pages (from-to)20/3
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume257
Issue number3
StatePublished - 1989

All Science Journal Classification (ASJC) codes

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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