Role of 5-HT in cholera toxin-induced mucin secretion in the rat small intestine.
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. Neither the 5-HT2 receptor antagonist ketanserin nor the cyclooxygenase inhibitor indomethacin was capable of inhibiting choleraic mucin secretion. However, in the presence of the mixed 5-HT3/4 receptor antagonist tropisetron at doses that block both receptor subtypes, the secretory response was reduced to baseline levels in 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 is mediated by a 5-HT4-like receptor and is capsaicin sensitive but tetrodotoxin (TTX) insensitive, and one 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.
Moore
B A
BA
Gastrointestinal Research Group, Faculty of Medicine, University of Calgary, Alberta, Canada.
Sharkey
K A
KA
Mantle
M
M
D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D002772:Cholera Toxin / Q000494:pharmacology*; D007211:Indoles / Q000494:pharmacology; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009077:Mucins / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology; D000077526:Tropisetron
D007211:Indoles; D009077:Mucins; D012702:Serotonin Antagonists; D012701:Serotonin; D013779:Tetrodotoxin; D000077526:Tropisetron; D002772:Cholera Toxin; D002211:Capsaicin