Hindbrain effects of pituitary adenylate cyclase-activating
polypeptide on gastric motor function in the rat.
Krowicki, Zbigniew K., Akira Arimura, Nicole A. Nathan, and Pamela J.
Hornby.
Department of Pharmacology and Experimental Therapeutics, Louisiana
State University Medical Center, New Orleans, LA 70112, U.S.-Japan
Biomedical Research Laboratories, Tulane University Hebert Center,
Belle Chasse, LA 70037
APStracts 3:0272G, 1996.
Pituitary adenylate cyclase-activating polypeptide (PACAP)-like
immunoreactive cell bodies and fibers are visualized in hindbrain
nuclei that are involved in the regulation of autonomic function, and
yet little is known about the gastric and cardiovascular effects of
this peptide in the dorsal vagal complex, the nucleus raphe obscurus
and nucleus ambiguus. Therefore, multiple-barreled micropipettes were
used to inject PACAP38 (1-100 pmol) into each of these nuclei in
"-chloralose anesthetized rats, while recording intragastric
pressure, pyloric and greater curvature smooth muscle contractile
activity, blood pressure, and heart rate. For comparison, the effect
of L-glutamate (15 nmol) microinjected into the same sites on gastric
motor activity was also assessed. L-Glutamate microinjected into each
nucleus prior to PACAP38, significantly increased intragastric
pressure, both in terms of the peak increase and the total area of
the response. Microinjections of PACAP38 (10 and 100 pmol) into each
of the nuclei significantly increased peak intragastric pressure, but
the total area of the response was only significantly increased by
the highest dose (100 pmol) in the case of the dorsal vagal complex
and nucleus raphe obscurus. No consistent changes in heart rate and
mean arterial blood pressure were noted after microinjection of
PACAP38 into each of the three nuclei. Bilateral vagotomy abolished
the increase in intragastric pressure in response to microinjection
of PACAP38 into the dorsal vagal complex and nucleus raphe obscurus.
Overall, we conclude that PACAP38 in the dorsal vagal complex,
nucleus raphe obscurus and nucleus ambiguus is involved in vagally
-mediated gastric motor excitation.
Received 30 July 1996; accepted in final form 20 November 1996.
APS Manuscript Number G304-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996