AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 5 541-R548, Copyright © 1985 by American Physiological Society
Central effects of angiotensin II and dopamine in sodium-depleted sheep
B. S. Huang, R. L. Malvin and R. J. Grekin
The effects of intracerebroventricular (IVT) infusion of angiotensin II
(ANG II), the converting enzyme inhibitor SQ 20881, and dopamine were
studied in 15 conscious Na-depleted sheep. IVT ANG II (25 ng/min)
significantly increased plasma aldosterone (163 +/- 24%) and vasopressin
(ADH) (533 +/- 100%). Plasma renin activity (PRA) was decreased to 64 +/-
10% of basal. IVT SQ (1 microgram/min) decreased aldosterone to 70 +/- 10%
and ADH to 55 +/- 9% of basal. PRA increased to 124 +/- 10%. There were no
significant changes in plasma Na, K, or cortisol levels nor in mean
arterial or intracranial pressure after either infusion. Increasing the
dose of SQ to 10 micrograms/min resulted in an increased magnitude of
change in the same variables. IVT SQ (1 microgram/min) significantly
decreased aldosterone level in five nephrectomized sheep. The responses to
IVT dopamine (20 micrograms/min) were qualitatively similar to those
elicited by IVT SQ. These data support the existence of an endogenous brain
renin-angiotensin system (RAS) independent of the renal RAS. ANG II acts
centrally to regulate plasma ADH, aldosterone, and PRA levels. The
similarity of the responses to SQ and dopamine suggests that a dopaminergic
pathway may be involved in these responses.
