Role of alpha-2 adrenoceptors in regulation of giant migrating contractions and defecation in conscious dogs

Munenori Nagao, Chikashi Shibata, Yuji Funayama, Kouhei Fukushima, Ken Ichi Takahashi, Xue Lin Jin, Katsuyoshi Kudoh, Iwao Sasaki

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

The aim was to investigate the effects of α2-adrenoceptor antagonsist yohimbine on colonic motility and defecation. The effects of yohimbine (0.5, 1.0, and 3.0 mg/kg) on colonic motility and defecation were studied in neurally intact dogs (N=6), dogs with extrinsic denervation of the ileocolon (N=4), and dogs with enterically isolated ileocolnic loops (N=5) equipped with strain gauge force transducers on the ileocolon. The effects of yohimbine on colonic motility and defecation were also studied in the presence of various antagonists (atropine, hexamethonium, ondansetron, FK224, and naloxone). Yohimbine evoked giant migrating contractions and defecation in a dose-independent manner in neurally intact dogs. These stimulatory effects of yohimbine were abolished by atropine and hexamethonium. In dogs with extrinsic denervation, yohimbine induced giant migrating contractions in the colon but did not stimulate defecation. In dogs with ileocolonic loops, yohimbine induced colonic motor complexes but not giant migrating contractions in the enterically isolated colon. These results indicate that α2-adrenoceptors in the peripheral nervous system regulate giant migrating contractions by controlling the release of acetylcholine, while those in the central nervous system must be important in the regulation of defecation.

Original languageEnglish
Pages (from-to)2204-2210
Number of pages7
JournalDigestive Diseases and Sciences
Volume52
Issue number9
DOIs
Publication statusPublished - 2007 Sep

Keywords

  • Defecation
  • Extrinsic denervation
  • Giant migrating contractions
  • Ileocolonic loop
  • Yohimbine

ASJC Scopus subject areas

  • Physiology
  • Gastroenterology

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