AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 1 284-R291, Copyright © 1994 by American Physiological Society
Serotonin contracts the isolated rat pylorus via a 5-HT2-like receptor
K. Eberle-Wang, B. T. Braun and K. J. Simansky
Department of Pharmacology, Medical College of Pennsylvania, Eastern Pennsylvania Psychiatric Institute, Philadelphia 19129.
Serotonin (5-HT) produced concentration-dependent contractions of the
isolated rat pylorus in vitro. Serotonergic contractions were antagonized
by the calcium L-channel blocker, diltiazem, but not by tetrodotoxin or
atropine. Three drugs that block 5-HT2 receptors, ketanserin, xylamidine,
and methysergide, unsurmountably inhibited contractions to 5-HT. In
contrast, antagonists of 5-HT3, 5-HT1A/1B, beta-adrenergic, or alpha
1-adrenergic receptors did not alter the response to 5-HT. Devazepide, an
antagonist of cholecystokinin (CCK) type-A receptors, blocked contraction
produced by CCK-8 but not by 5-HT. Conversely, the 5-HT2 antagonists did
not affect CCK-stimulated contraction. These results suggest that 5-HT
contracts the pylorus by a 5-HT2-like receptor on muscle and that this
response occurs independently of CCKergic receptor mechanisms. Furthermore,
the parallel between the overall pharmacological profile for serotonergic
contraction of the pylorus and that observed previously for the anorectic
action of peripheral 5-HT makes the pylorus a logical candidate for
peripheral serotonergic control of feeding.
