APStracts 2:0014R, 1995.

Serotonin enhances gastric acid response to trh analog in the dorsal vagal complex through 5-ht2 receptors in rats. Yoneda, Masashi, and Yvette Tache. CURE/Gastroenteric Biology Center, VA Gastroenteric Biology Center, VA Wadsworth Medical Center, Department of Medicine and Brain Research Institute, University of California, Los Angeles, CA, 90073, U.S.A.

APStracts 2:0014R, 1995.

Serotonin enhances gastric acid response to TRH analog in the dorsal vagal complex through 5-HT2 receptors in rats. Am. J. Physiol. (Regulatory Integrative Physiol.)- The effect of serotonin (5-HT) and TRH analog, RX 77368, injected into the dorsal vagal complex (DVC) on gastric acid secretion was assessed in urethan-anesthetized rats with gastric cannula. 5-HT (0.1, 0.2, 1 or 10 nmol into the DVC) enhanced by 54%, 100%, 147% and 144% respectively the acid response to RX 77368 (25 pmol, DVC) while given alone 5- HT had no effect. The 5-HT2 receptor agonists (1 nmol, DVC), DOI, TFMPP, and [alpha]-methyl-5-HT increased by 153%, 108%, and 96% respectively the gastric acid response to co-injection of RX 77368 (25 pmol) whereas 8-OH-DPAT (5- HT1A), CGS 12066 (5 -HT1A/1B), and 2-methyl-5-HT (5-HT3) did not. The 5-HT2 receptor antagonist, ketanserin (20 nmol), injected intracisternally abolished the potentiating action of 5-HT injected into the DVC with RX 77368 while the 5-HT antagonists, spiperone (5-HT2/1A) and ondansetron (5-HT3) did not. Ketanserin (1 nmol/site bilaterally into the DVC) decreased by 62% the acid response to kainic acid injected into the raphe pallidus. These data suggest that 5-HT acting at 5-HT2 receptors in the DVC potentiates the gastric acid response to exogenous and endogenous TRH.

Received 6 September 1994; accepted in final form 11 January 1995.
APS Manuscript Number R500-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative Comp.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.