5-HT-induced jejunal motor activity: Enteric locus of action and receptor subtypes

Stefanie Graf, Sushil K. Sarna

Research output: Contribution to journalArticle

26 Scopus citations

Abstract

The role of 5-hydroxytryptamine (5-HT), its enteric locus of action, and receptor subtypes involved in the regulation of jejunal contractions were investigated by close intra-arterial infusions in conscious dogs. Close intra-arterial infusions of 5-HT in short segments of the jejunum stimulated phasic contractions that were blocked completely by atropine, partially by tetrodotoxin, and not affected by hexamethonium. This response was also blocked significantly by 5-HT(2A) and 5-HT(2C) receptor antagonists but was not affected by 5-HT(1A)/5-HT(1B), 5-HT3, and 5-HT4 receptor antagonists. Spontaneous phase III contractions were inhibited significantly by 5-HT(2A) and 5-HT(2C) receptor antagonists, not affected by 5-HT(1A)/5-HT(1B) and 5- HT3 receptor antagonists, and enhanced by 5-HT4 receptor antagonists. Repeated close intra-arterial infusions of 5-HT over several days stimulated giant migrating contractions. We conclude that in the conscious state, 5-HT acts on 5-HT(2A) and 5-HT(2C) receptors located on postsynaptic cholinergic neurons in the canine jejunum to stimulate phasic contractions and phase III activity. The 5-HT4 receptors in the canine small intestine may be localized on nonadrenergic, noncholinergic inhibitory neurons; these receptors suppress the amplitude and duration of phase III activity.

Original languageEnglish (US)
Pages (from-to)G992-G1000
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume270
Issue number6 33-6
StatePublished - Jun 1 1996

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Keywords

  • 5-hydroxytryptamine
  • gastrointestinal motility
  • methysergide
  • mianserin
  • ondansetron
  • pindolol
  • tropisetron

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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