AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 6 1274-R1280, Copyright © 1990 by American Physiological Society
Effect of sympathectomy on renal and circulatory action of atrial natriuretic peptide
D. E. Allen
Physiology Program, School of Life and Health Sciences, University of Delaware, Newark 19716.
Sympathetic nervous system (SNS) involvement in cardiovascular (CV) and
renal actions of atrial natriuretic peptide (ANP) was examined in eight
chronically instrumented rats. Responses to 90-min atriopeptin II infusion
(0.03 then 0.3 micrograms.kg-1.min-1) were compared with those to sodium
nitroprusside (NP; 2 + 20 micrograms.kg-1.min-1) before and after
sympathectomy (SX) with 6-hydroxydopamine (6-OHDA). The NP-induced drop in
blood pressure (BP) was greater after SX (-12 +/- 1% before vs. -24 +/- 2%
after SX). In contrast, 6-OHDA altered (blunted) only the bradycardic
response to high dose of ANP (-23 +/- 5% before vs. -3 +/- 4% after SX).
The decreased BP (-18 +/- 1% before vs. -12 +/- 2% after), depressed
cardiac output (CO; -29 +/- 1% before vs. -22 +/- 3% after), and elevated
systemic vascular resistance (SVR; 16 +/- 2 vs. 16 +/- 6%) were unchanged
(paired t test, P greater than 0.05). The high dose of ANP increased urine
flow by 43.2 +/- 7.2 microliters.min-1.100 g body wt-1 and sodium excretion
by 1.76 +/- 0.56 mu eq.min-1.100 g body wt-1 but had no effect after SX.
These results suggest that while withdrawal of SNS activity contributes to
the CO-lowering effect of ANP, it does not mediate its action to elevate
SVR. Attenuation of the capacity for reflex sympathoexcitation by SX did
not reveal a vasodilator action. The lack of response after SX suggests
that ANP's renal excretory actions are mediated in part by withdrawal of
SNS activity.
