Nonuniform sympathetic nerve responses following sustained elevation in arterial pressure. Claassen, Dale E., Donald A. Morgan, Tadakazu Hirai, and Michael J. Kenney. Department of Anatomy and Physiology, Kansas State University, Manhattan, KS 66506; Department of Internal Medicine, Cardiovascular Center, University of Iowa College of Medicine and Veterans Affairs Medical Center, University of Iowa, Iowa City, IA 52242.
APStracts 3:0172R, 1996.
We tested the hypothesis that sustained increases in mean arterial pressure (MAP) produce nonuniform changes in regional sympathetic nerve discharges (SND) following the return of MAP to control levels. Renal, adrenal, splanchnic, and lumbar SND were recorded before, during and after a 30-min elevation in MAP produced by phenylephrine (PE) infusion in chloralose-anesthetized, spontaneously hypertensive (SH) rats. SND remained reduced from control values following PE infusion, despite the return of MAP to control levels. Importantly, the duration of poststimulus sympathoinhibition was significantly less in adrenal and splanchnic SND compared to renal and lumbar SND. In sinoaortic denervated SH rats, SND remained at control levels during and after PE infusion. Simultaneous recordings of aortic depressor nerve (ADN) activity and SND demonstrated that prolonged renal and lumbar sympathoinhibition occurred even when ADN activity fell below control levels after PE infusion. We conclude that poststimulus responses of efferent SND in SH rats are regionally nonuniform, and that renal and lumbar sympathoinhibitory responses are not mediated solely by prolonged increases in afferent baroreceptor nerve activity. 

Received 23 October 1995; accepted in final form 23 April 1996.
APS Manuscript Number R659-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 8 May 96