5-HT-induced colonic contractions: Enteric locus of action and receptor subtypes

Stefanie Graf, Sushil K. Sarna

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


The role of 5-hydroxytryptamine (5HT), its enteric locus of action, and the receptor subtypes involved in the stimulation of in vivo phasic contractions in the colon were investigated by close intra-arterial infusions in conscious dogs. The contractile response to 5-HT was blocked completely by prior close intra-arterial infusion of atropine and reduced significantly by prior close intra-arterial infusions of tetrodotoxin and hexamethonium. The contractile response was, however, enhanced by the inhibition of nitric oxide (NO) synthase by a prior close intra-arterial infusion of N(ω)-nitro-L- arginine methyl ester. Prior close intra-arterial infusions of 5-HT(1A)/5- HT(1B), 5-HT(2A), 5-HT(2C), and 5-HT4 receptor antagonists had no significant effect on the contractile response to 5-HT. By contrast, 5-HT3 receptor antagonist significantly and dose dependently inhibited the contractile response to 5-HT. We conclude that the in vivo phasic contractile response to 5-HT in the colon is mediated mainly by 5-HT3 receptors located on pre- and postsynaptic cholinergic enteric neurons. 5-HT receptors may also be localized on nonadrenergic, noncholinergic inhibitory motoneurons that use NO as a neurotransmitter.

Original languageEnglish (US)
Pages (from-to)G68-G74
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Issue number1 36-1
StatePublished - Jul 1997


  • 5-hydroxytryptamine
  • 5-hydroxytryptamine receptors
  • Colon
  • Diarrhea
  • Granisetron
  • Methysergide
  • Serotonin

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)


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