Inhibition of stress‐stimulated colonic propulsion by α₂‐adrenoceptor antagonists in rats

Abstract

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.

l -Lysine acts like a partial serotonin receptor 4 antagonist and inhibits serotonin-mediated intestinal pathologies and anxiety in rats

“…The time dependence is identical with that found in rats and humans after treatment with two chemically distinct 5-HT 4 receptor antagonists (4,12,34,35). Additionally, chronic Lys nutritional deficiency increased stress-induced defecation during the second, but neither the first nor the third hour of wrap-restraint stress (24).…”

Inhibitory Effects of Ramosetron, a Potent and Selective 5-HT3–Receptor Antagonist, on Conditioned Fear Stress–Induced Abnormal Defecation and Normal Defecation in Rats: Comparative Studies With Antidiarrheal and Spasmolytic Agents

“…These results, and literature reports, indicate that muscarinic receptors mediate both normal defecation and stressinduced abnormal defecation, whereas 5-HT 3 receptors are involved in stress-induced abnormal defecation but not in normal defecation. In contrast, it has been previously reported that ramosetron significantly inhibited normal colonic transit as well as wrap-restraint stress-stimulated defecation and colonic transit in rats (26). The literature showed that ramosetron at doses of 3 µg/ kg or more completely abolished the wrap stress-stimulated colonic transit but inhibited the wrap stress-stimulated defecation to approximately 50% -60% of control rats.…”

Electroacupuncture at ST-36 accelerates colonic motility and transit in freely moving conscious rats

“…Colonic transit and fecal expulsion are stimulated by a variety of acute stresses (18,33,44,54). Restraint stress upregulates c-Fos expression in the CNS (12,31).…”