Inhibition of nitric oxide synthase in the brain suppresses colonic
motor activity.
Ohta, Daisaku, Sushil K. Sarna, Robert E. Condon, and Ivan M. Lang.
Departments of Surgery, Physiology and Medicine, and Digestive
Disease Research Center, Medical College of Wisconsin and Zablocki VA
Medical Center, Milwaukee, Wisconsin 53295, USA
APStracts 2:0238G, 1995.
The effects of inhibition of nitric oxide (NO) synthase in the brain
on colonic motor activity was investigated in conscious dogs.
Intracerebroventricular (ICV) infusion of N -nitro-L-arginine methyl
ester (L-NAME ) and N -nitro-L-arginine (L-NNA) significantly
suppressed colonic motor activity. The inhibitory effects occurred
one hour after the end of the infusion and lasted for at least 4 h.
This suppression was blocked by a concurrent infusion of L-arginine
but not D-arginine. The suppression of colonic motor activity was not
blocked by bilateral truncal vagotomy or intravenous administration
of phentolamine, an [alpha]-receptor antagonist and propranolol, a
[beta]-receptor antagonist. ICV infusion of L-NAME had no significant
effect on the occurrence of giant migrating contractions in the
colon. By contrast, intravenous administration of L-NAME at higher
doses significantly enhanced colonic motor activity. We conclude that
the inhibition of NO synthesis in the brain suppresses, whereas the
inhibition of NO synthesis in peripheral neurons stimulates colonic
motor activity. The central effect may be mediated by decrease in
cerebral blood flow due to the inhibition of NO synthesis in cerebral
arteries.
Received 14 March 1995; accepted in final form 18 October 1995.
APS Manuscript Number G110-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95