Vagal hepato-pancreatic reflex effect evoked by intraportal appearance of truncated glucagon-like peptide-1. Nakabayashi, Hajime, Makoto Nishizawa, Atsushi Nakagawa, Ryoyu Takeda, and Akira Niijima. Department of Internal Medicine (II), School of Medicine, Kanazawa University, Kanazawa 920; and Department of Physiology, Niigata University School of Medicine, Niigata 951, Japan
APStracts 3:0148E, 1996.
Among proglucagon-derived peptides, truncated form of glucagon-like peptide-1, GLP-1(7-36)amide (tGLP-1), is known as most likely physiological humoral incretin. To examine whether there exists any relationship between tGLP-1 levels in the portal vein and activities of the hepatic and pancreatic vagal system, changes of the impulse discharge rate in the hepatic afferent vagus and the pancreatic efferent vagus upon intraportal tGLP-1 injection were measured in situ in rats anesthetized with urethan and chloralose. First, 1-min bolus tGLP-1 injection at a periphysiological dose of 0.2 pmol or a pharmacological dose of 4.0 pmol, but not the vehicle injection, significantly facilitated the hepatic vagal afferents for more than 90 min, showing weaker facilitation at 0.05 pmol dose. Notably, the injection of non-insulinotropic full length GLP-1 failed to facilitate the afferents at 4.0 or 40.0 pmol dose. Second, the intraportal tGLP-1 injections at 0.05 and 0.2 pmol dose facilitated marginally and significantly the pancreatic vagal efferents in normal rats, respectively, but not at all in the hepatic vagotomized rats at even 40.0 pmol dose. The present results indicate that an intraportal appearance of tGLP-1 is specifically recognized by the hepatic vagal nerve and this recognition further augments the pancreatic vagal efferent activity in a reflex way, suggesting another nature of tGLP -1 as neuroincretin in the entero-insular axis. 

Received 16 April 1996; accepted in final form 11 July 1996.
APS Manuscript Number E186-6.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 25 July 1996