AJP - Gastrointestinal and Liver Physiology, Vol 270, Issue 1 20-G28, Copyright © 1996 by American Physiological Society
Role of endogenous 5-hydroxytryptamine in the regulation of gastric contractions by motilin in dogs
N. Haga, A. Mizumoto, M. Satoh, E. Mochiki, F. Mizusawa, K. Ohshima and Z. Itoh
Gastrointestinal Research Laboratories, Gunma University, Maebashi, Japan.
It has been suggested that 5-hydroxytryptamine3 (5-HT3) receptors are
involved in the control of phase III contractions in the stomach. We
examined the effect of depletion of endogenous 5-HT by
p-chlorophenylalanine (pCPA) on spontaneously and motilin-induced phase III
contractions in conscious dogs, and the effect of 5,6-dihydroxytryptamine
(5,6-DHT) in an isolated perfused dog stomach. Three-day treatment with
pCPA significantly reduced plasma 5-HT concentration and 5-HT content in
the stomach, and strongly suppressed the spontaneous and motilin-induced
phase III contractions in the stomach. When spontaneous phase III
contractions recovered in the stomach after a 3-day treatment, exogenous
motilin induced typical phase III-like contractions, and the 5-HT content
in the muscle layer was recovered to the normal pretreatment level. In the
perfused stomach, 5,6-DHT decreased 5-HT content in the muscle layer alone
and abolished motilin-induced contractions. In conclusion, endogenous 5-HT,
probably in 5-HT neurons, plays an important role in the control of
interdigestive phase III activity by motilin in the stomach.
