Involvement of endogenous nitric oxide in the regulation of distal colonic motility in anaesthetized rat.

The contribution of the endogenous nitric oxide (NO) to the distal colonic motility was investigated by inhibiting NO production using NO synthase inhibitor, NG-monomethyl-L-arginine (L-NMMA). The experiment was carried out in the anaesthetized rat, which was vagotomized and pretreated with guanethidine, phentolamine and propranolol. The colonic motility was evaluated by changes in the increase in intraluminal pressure of the distal colon. L-NMMA infusion (100mg/kg iv) in the presence of atropine (1 mg/kg iv) resulted in a significant increase in arterial blood pressure and intraluminal pressure. The following L-arginine infusion (100mg/kg iv) restored blood pressure and intraluminal pressure to the control level. In contrast, L-NMMA infusion in the absence of atropine resulted in no change in intraluminal pressure with a significant increase in arterial blood pressure. These results indicate that there are NO-dependent and nondependent mechanisms to regulate the distal colonic motility.