Effects of cerebral trh on intestinal water transport: role of
vagal, muscarinic and vip pathways.
Lenz, H. J[umlaut]urgen, and Thomas A. Silverman.
Departments of Medicine and Physiology, University of California,
San Diego, La Jolla, California 92093-0671 and University of Hamburg,
Hamburg, Federal Republic of Germany
APStracts 2:0027G, 1995.
Thyrotropin-releasing hormone (TRH) is a central nervous system (CNS)
transmitter that stimulates various gastrointestinal secretory and
motor processes by increasing vagal outflow. In this study, the CNS
effects of TRH on ileal and jejunal water transport were examined in
awake rats and dogs, respectively. Cerebral but not intravenous TRH
(0.1-5.0 nmol/kg) significantly (P < 0.01) reversed net water
absorption from approximately 30 [mu]l/cm.h in rats and 300 [mu]l/cm.h in
dogs towards net water secretion of 60 and 600 [mu]l/cm.h, respectively.
Truncal vagotomy and ganglionic blockade with chlorisondamine
completely abolished this stimulatory effect of cerebral TRH while
adrenalectomy, hypophysectomy, noradrenergic and opiate blockade, and
inhibition of prostaglandin and nitric oxide synthesis did not.
Atropine methyl nitrate significantly (P < 0.05) attenuated the
stimulatory response produced by TRH by approximately 30%.
Intravenous infusion of the VIP receptor antagonist, [4Cl-D-Phe6,
Leu17]VIP (0.05-5.0 [mu]mol/kg.h) significantly (P < 0.01) inhibited
the stimulatory response of TRH by approximately 60%. Pretreatment of
the animals with both atropine and the VIP antagonist completely
abolished ileal and jejunal water secretion stimulated by cerebral
TRH. These results indicate: 1. TRH acts within the CNS to stimulate
net ileal and jejunal water secretion in rats and dogs, respectively.
2. These actions are mediated by vagal pathways. 3. Stimulation of
intestinal secretion by cerebral TRH is primarily mediated by a VIP
-sensitive and, in part, by a muscarinic mechanism.
Received 20 May 1994; accepted in final form 9 February 1995.
APS Manuscript Number G190-4.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 23 February 1995.