The role of 5-hydroxytryptamine (5-ht) in cholera toxin-induced
mucin secretion in the rat small intestine.
Moore, Beverley A., Keith A. Sharkey, and Mich[grave]ele Mantle.
Gastrointestinal and Neuroscience* Research Groups, Faculty of
Medicine, University of Calgary, Calgary, Alberta, T2N 4N1,
Canada
APStracts 3:0004G, 1996.
We examined the role of 5-hydroxytryptamine (5-HT) in cholera toxin
(CT)-induced mucin secretion in the proximal and distal regions of
the rat small intestine. Results showed that neither the 5-HT2
receptor antagonist ketanserin nor the cyclooxygenase inhibitor
indomethacin were capable of inhibiting choleraic mucin secretion.
However, in the presence of the mixed 5-HT3/4 receptor antagonist
tropisetron at doses which block both receptor subtypes, the
secretory response was reduced to baseline levels in the both the
proximal and distal small intestine. The selective 5-HT3 receptor
antagonist ondansetron had no significant effect. These findings
suggest that choleraic mucin secretion is mediated primarily through
the activation of a 5-HT4-like receptor. Mucin secretion in response
to the exogenous application of 5-HT occurs via two pathways; one
which is mediated by a 5-HT4-like receptor and which is capsaicin
-sensitive but TTX-insensitive; and one which lacks the capsaicin
-sensitive, 5-HT4-mediated response but is TTX-sensitive. Both
converge on a common pathway that is cholinergic. No significant
differences were observed between proximal and distal intestinal
segments.
Received 12 May 1995; accepted in final form 17 November 1995.
APS Manuscript Number G200-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 22 January 96