AJP - Heart and Circulatory Physiology, Vol 256, Issue 1 1-H8, Copyright © 1989 by American Physiological Society
Synergism of intraventricular NaCl infusion and subpressor angiotensins in rats
K. Katahira, H. Mikami, T. Ogihara, K. Kohara, A. Otsuka, Y. Kumahara and M. C. Khosla
Department of Medicine and Geriatrics, Osaka University Medical School, Japan.
The effect of selective salt infusion to the central nervous system on the
blood pressure (BP) regulation was examined in male Wistar rats. Hypertonic
NaCl (0.8 M, 1 microliter/h) was infused into the lateral ventricle
concomitantly with intravenous infusion of a subpressor dose (5.4
pmol.kg-1.min-1) of angiotensin II (ANG II) or its analogues for 7 days
using osmotic minipumps. The BP was not increased by
intracerebroventricular infusion of NaCl alone at this dose but was
significantly and consistently increased by concomitant intravenous
infusion of ANG II or its analogues. The increases in the BP over the
base-line values on day 7 in groups on infusions of ANG II, ANG III, and
pentasarcosyl-ANG II [(Sar)5ANG II] were 29 +/- 5 mmHg (n = 9, P less than
0.05), 8 +/- 2 mmHg (n = 8, P less than 0.05), and 19 +/- 3 mmHg (n = 6, P
less than 0.05), respectively. The responses to hexamethonium, prazosin,
and antagonists of arginine vasopressin and ANG II were examined in
separate sets of conscious and unrestrained animals that had received
intracerebroventricular infusion of NaCl and intravenous infusion of ANG II
for the preceding 6 days. These animals showed significantly greater
depressor responses only to hexamethonium and prazosin than control. These
results indicate that the pressor effect of continuous and concomitant
administration of intracerebroventricular NaCl and intravenous ANG II is
mainly due to activation of the sympathetic nerve function. Synergism of
the effects of selective central sodium administration and a subpressor
dose of ANG II in the central nervous system is suggested.
