Inhibition of nitric oxide (NO) synthase on plasma motilin concentrati
ons is not known. The aim of this study was to examine the effect of N
O synthesis inhibitor on gastrointestinal motility and motilin release
in conscious dogs. Dogs fitted with force transducers were given N-om
ega-nitro-L-arginine (L-NNA) after the termination of phase III contra
ctions. Blood samples were taken for measurement of motilin concentrat
ions. L-NNA induced phase III-Iike contractions in the stomach and duo
denum in association with a significant increase in motilin level. Atr
opine or hexamethonium significantly inhibited L-NNA-induced phase III
-like contractions and the increase in motilin level. Ondansetron mark
edly inhibited gastric, but not duodenal, phase III-Iike contractions
without affecting the increase in motilin level caused by L-NNA. Vagot
omy affected neither the occurrence of phase III-like contractions nor
the increase in motilin level produced by L-NNA. We conclude that inh
ibition of NO synthesis stimulates motilin release via cholinergic pat
hways independent of the vagus, and induces phase III-like contraction
s in the stomach and duodenum. Phase III-like contractions induced by
L-NNA are mediated through the activation of 5-HT3 receptors. (C) 1997
Elsevier Science B.V.