Neural reflexes controlling intestinal microcirculation. Vanner, Stephen, and Annmarie Surprenant. Depts. Medicine, Physiology, and Biology, Queen's University, Kingston, Ontario, Canada, Glaxo Institute for Molecular Biology, Geneva, Switzerland
APStracts 3:0086G, 1996.
It has long been established that neural reflexes are involved in the regulation of gastrointestinal vascular function, in particular the mucosal hyperemia that follows food ingestion. However, more precise identification of reflex pathways involved in the control of mucosal blood flow had not been forthcoming because of lack of adequate methods to examine resistance arterioles within the intestinal wall. Recent advances have employed novel in vitro preparations and videomicroscopic techniques to investigate the neural control of the GI microvasculature and involvement of intrinsic and extrinsic vasodilatory neurones in mucosal reflexes. Vasoconstrictor innervation to submucosal arterioles is mediated solely by extrinsic sympathetic nerves which release ATP onto arteriolar P2x -purinoceptors. Neurogenic vasodilation of submucosal arterioles occurs by release of acetylcholine and/or neuropeptides from intrinsic submucosal neurones as well as by release of substance P and calcitonin gene related peptide from extrinsic sensory nerves. Both vasodilator pathways can be activated independently by mucosal stimulation and both have afferent and efferent components confined to the mucosa and submucosal neuronal plexus. We speculate that the intrinsic enteric cholinergic reflex pathways are involved in local physiological control of mucosal blood flow whereas extrinsic sensory reflex pathways are preferentially activated during inflammatory states. 

Received 10 January 1996; accepted in final form 26 March 1996.
APS Manuscript Number G117-6.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 1 May 96