AJP - Heart and Circulatory Physiology, Vol 268, Issue 1 61-H67, Copyright © 1995 by American Physiological Society
Dietary Na+ and cardiopulmonary baroreflex control of renal sympathetic nerve activity in SHR
B. S. Huang and F. H. Leenen
Hypertension Unit, University of Ottawa Heart Institute, Ontario, Canada.
In young Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR)
with or without chronic sinoaortic denervation (SAD), we evaluated the
effects of low, regular, and high dietary sodium intake (L-Na, R-Na, and
H-Na, respectively) from 4 to 8 wk of age on cardiopulmonary baroreflex
function, which was assessed by changes in renal sympathetic nerve activity
(RSNA) and heart rate (HR) in response to acute volume expansion. In intact
SHR H-Na increased blood pressure (BP), whereas L-Na decreased BP. No
changes were observed in intact WKY. The gain of the cardiopulmonary
baroreflex control of both HR and RSNA was significantly attenuated in SHR
vs. WKY on R-Na. In both SHR and WKY, L-Na had no effects on the gain of
RSNA and HR responses. In both strains, H-Na did not affect the gain of HR
but attenuated the gain of the RSNA response. H-Na attenuated the gain of
RSNA response more in SHR with SAD vs. intact SHR (52 vs. 69% of
corresponding R-Na control) but less in WKY with SAD vs. intact WKY (80 vs.
71% of corresponding R-Na control). These data indicate that in SHR, H-Na
further desensitizes the already impaired cardiopulmonary baroreflex
control of RSNA. After SAD, this attenuation is more prominent in SHR but
becomes less prominent in WKY. High sodium intake, therefore, modulates the
interaction between the arterial and cardiopulmonary baroreflexes in the
control of RSNA oppositely in WKY vs. SHR.
