Inhibition of stress-stimulated colonic propulsion by alpha 2-adrenoceptor antagonists in rats.
Alpha2-adrenoceptor antagonists have been reported to stimulate colonic motor activity, but the effect on colonic motor dysfunction is unclear. We have investigated the effect of alpha 2-adrenoceptor antagonists on wrap-restraint stress-stimulated and normal colonic propulsion in rats. Colonic propulsion was evaluated by the transit of a charcoal marker along the colon. Faecal pellets output was also measured. A 30-min exposure to wrap-restraint stress starting 120 min after infusion of the charcoal marker significantly stimulated colonic transit with a concomitant increase in faecal pellets. Yohimbine and idazoxan, alpha 2-adrenoceptor antagonists, clonidine, an alpha 2-adrenoceptor agonist, and atropine suppressed wrap-restraint stress-stimulated colonic transit and faecal excretion in a dose-dependent manner. Ondansetron and YM060, 5-hydroxytryptamine3 (5-HT3) receptor antagonists, potently inhibited wrap-restraint stress-stimulated colonic transit, but only weakly inhibited faecal excretion. Neither alpha 2-adrenoceptor antagonists nor atropine had any significant effect on normal colonic transit, whereas clonidine and the 5-HT3 receptor antagonists inhibited it. alpha 2-Adrenoceptor antagonists as well as clonidine, atropine and 5-HT3 receptor antagonists inhibit the stress-induced colonic motor dysfunction in rats.
Yamamoto
O
O
Research Laboratories, Nippon Shinyaku Co. Ltd, Kyoto, Japan.
Niida
H
H
Tajima
K
K
Shirouchi
Y
Y
Masui
Y
Y
Ueda
F
F
Kise
M
M
Kimura
K
K
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D003106:Colon / Q000187:drug effects* / Q000503:physiopathology*; D003672:Defecation / Q000187:drug effects / Q000502:physiology; D005769:Gastrointestinal Motility / Q000187:drug effects* / Q000502:physiology*; D005772:Gastrointestinal Transit / Q000187:drug effects; D019329:Idazoxan / Q000494:pharmacology; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012702:Serotonin Antagonists / Q000494:pharmacology; D013312:Stress, Physiological / Q000503:physiopathology*; D015016:Yohimbine / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D012702:Serotonin Antagonists; D015016:Yohimbine; D001285:Atropine; D003000:Clonidine; D019329:Idazoxan