AJP - Regulatory, Integrative and Comparative Physiology, Vol 268, Issue 6 1500-R1506, Copyright © 1995 by American Physiological Society
Central ANG II-receptor antagonists impair cardiovascular and vasopressin response to hemorrhage in rats
W. J. Lee, E. K. Yang, D. K. Ahn, Y. Y. Park, J. S. Park and H. J. Kim
Department of Physiology, School of Medicine, Kyungpook National University, Taegu, Korea.
The role of brain angiotensin II (ANG II) in mediating cardiovascular,
vasopressin, and renin responses to hemorrhage was assessed in conscious
spontaneously hypertensive rats (SHR) and in normotensive Wistar-Kyoto
(WKY) and Wistar rats. Intracerebroventricular administration of losartan
(10 micrograms) and saralasin (1 microgram.microliter-1.min-1) produced a
markedly greater fall in blood pressure and a reduced tachycardia during
and after hemorrhage (15 ml/kg) compared with the artificial cerebrospinal
fluid control in SHR and Wistar rats but not in WKY rats. Vasopressin
release after hemorrhage was also impaired, but renin release was enhanced
by intracerebroventricular ANG II antagonists in SHR and Wistar rats but
not in WKY rats. Losartan and saralasin produced remarkably similar effects
on the cardiovascular, vasopressin, and renin responses to hemorrhage.
These data suggest that brain ANG II acting through AT1 receptors plays an
important physiological role in mediating rapid cardiovascular regulation
and vasopressin release in response to hemorrhage. The relative importance
of brain angiotensin system may vary in different strains of rate.
