title: Effect of clonidine on colonic motility in rats.
abstract: Clonidine, an alpha(2)-adrenoceptor agonist, has been reported to inhibit gastric and small intestinal motility in rats. Whether clonidine also inhibits colonic motility is still not clear. The aim of this study was to examine the effect of clonidine on colonic motility and its possible site of action in adult Wistar rats. Colonic motilities in anesthetized rats in vivo or motilities of the isolated colon of rats in vitro were recorded. Clonidine was administered intravenously (i.v.) and intracerebroventricularly (i.c.v.) in vivo while bath administration was used in in vitro study. Clonidine i.v. or i.c.v. significantly inhibited colonic motility. This inhibitory effect was antagonized by pre-administration of yohimbine, an alpha(2)-adrenoceptor antagonist, but not by pre-administration of prazosin, an alpha(1)-adrenoceptor antagonist. Also, we have unpublished data indicating that the sympathectomy antagonized the inhibitory effect of systemically administered clonidine. A significant depression of colonic motility on the isolated colon was induced by bath administration of noradrenaline, while no such inhibition was seen by clonidine. The results of the present study suggested that clonidine inhibits colonic motility in rats through activation of central alpha(2)-adrenergic receptor.
authors.affiliation: Department of Physiology, School of Medical Sciences, Showa University, Hatanodai 1-5-8, Shinagawa, Tokyo 142-8555, Japan.
authors.forename: Teruyasu
authors.initials: T
authors.lastname: Umezawa
authors.forename: Shiyu
authors.initials: S
authors.lastname: Guo
authors.forename: Yongyi
authors.initials: Y
authors.lastname: Jiao
authors.forename: Tadashi
authors.initials: T
authors.lastname: Hisamitsu
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D003106:Colon / Q000187:drug effects* / Q000502:physiology; D004347:Drug Interactions; D005769:Gastrointestinal Motility / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D015016:Yohimbine; D003000:Clonidine; D009638:Norepinephrine; D011224:Prazosin