CENTRAL-NERVOUS-SYSTEM ACTION OF MELATONIN ON GASTRIC-ACID AND PEPSIN-SECRETION IN PYLORUS-LIGATED RATS

WE recently demonstrated that centrally administered melatonin at low doses inhibits the induction of gastric lesions by water-immersion res traint stress. To investigate the mechanism of the potent anti-ulcer a ction of melatonin, the central nervous system (CNS) effects of melato nin on gastric acid and pepsin secretion were studied in conscious pyl orus-ligated rats. Intracisternal (i.c.) melatonin (1-100 ng) dose-dep endently decreased acid and pepsin output, while a higher i.p. dose (1 mu g) had no inhibitory effect. The i.c. melatonin did not change ser um gastrin concentrations. Serum melatonin concentrations at 1 and 4h after i.c. administration of 10-100 ng melatonin did not differ from t hose in rats receiving i.c. vehicle. The present results suggest that melatonin administered centrally modulates the secretion of gastric ac id and pepsin which may explain, at least in part, the protective, ant i-stress role of melatonin in the gastric mucosa observed in our previ ous study. NeuroReport 9: 2447-2450 (C) 1998 Rapid Science Ltd.