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Updated: Aug 11, 2026

In Vitro Characterization of the Electrophysiological Properties of Colonic Afferent Fibers in Rats
Published on: September 27, 2017
Effect of alpha-2 adrenoceptor antagonists on colonic function in rats
O Yamamoto1, H Niida, K Tajima
1Discovery Research Laboratories, Nippon Shinyaku Co. Ltd., Nishiohji-Hachijo, Minami-ku, Kyoto, Japan. o.yamamoto@po.nippon-shinyaku.co.jp
Abstract:
We studied the effect of alpha-2 adrenoceptor antagonists on colonic function stimulated by water-avoidance stress, 5-hydroxytryptamine (5-HT), bethanechol and castor oil by comparison with the effects of atropine and a 5-hydroxytryptamine 3 (5-HT3) receptor antagonist, ondansetron. Yohimbine, idazoxan and atropine, but not ondansetron, significantly inhibited water-avoidance stress-stimulated faecal excretion. Yohimbine and idazoxan inhibited neither 5-HT- nor bethanechol-stimulated faecal excretion. In contrast, atropine inhibited both 5-HT- and bethanechol-stimulated faecal excretion and ondansetron inhibited 5-HT-stimulated faecal excretion. Yohimbine did not inhibit the incidence of diarrhoea induced by castor oil, but idazoxan significantly inhibited diarrhoea observed during a 1-h period after the administration of castor oil. Both atropine and ondansetron inhibited diarrhoea during a 2-h period after the administration of castor oil. These findings suggest that alpha-2 adrenoceptor antagonists specifically inhibit colonic motor function stimulated by stress in rats.
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