AJP - Gastrointestinal and Liver Physiology, Vol 273, Issue 1 68-G74, Copyright © 1997 by American Physiological Society

ARTICLES

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

S. Graf and S. K. Sarna
Department of Surgery, Medical College of Wisconsin, Milwaukee 53226, USA.

The role of 5-hydroxytryptamine (5-HT), 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 omega-nitro-L-arginine methyl ester. Prior close intra-arterial infusions of 5-HT1A/5-HT1B, 5-HT2A, 5-HT2C, 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.

This article has been cited by other articles:

				M. Li, C. P. Johnson, M. B. Adams, and S. K. Sarna Cholinergic and nitrergic regulation of in vivo giant migrating contractions in rat colon Am J Physiol Gastrointest Liver Physiol, September 1, 2002; 283(3): G544 - G552. [Abstract] [Full Text] [PDF]