AJP - Regulatory, Integrative and Comparative Physiology, Vol 242, Issue 3 318-R325, Copyright © 1982 by American Physiological Society
Central and peripheral adrenergic modulation of carotid sinus-induced renin release
H. D. Schultz, J. E. Zehr and A. Livnat
To study central and peripheral mechanisms that regulate the level of
circulating renin during activation of the carotid sinus baroreflex, both
carotid sinuses were isolated and perfused at constant flow in
chloralase-anesthetized dogs. Sinus pressure was controlled by an
adjustable reservoir while systemic pressure was stabilized using an
external chamber. Arterial renin activity, measured by radioimmunoassay,
was increased during sinus hypotension only if systemic pressure was held
constant. The renin response was eliminated by either sinus or renal
denervation. Administration of propranolol (iv) or phentolamine directly
into the renal artery totally blocked the increase in renin during
activation of the reflex. Perfusion of a beta-adrenergic blocker
(propranolol) or an alpha-adrenergic blocker (phentolamine) through the
third and fourth cerebroventricles had no effect on the increase in renin
during sinus hypotension, whereas centrally administered clonidine, and
alpha-agonist, blocked the response. We conclude that the sinus reflex arc
affecting renin release involves not only activation of peripheral alpha-
and beta-adrenergic receptors in the kidney but also inhibition of central
alpha-adrenergic receptors. No evidence for central beta-involvement was
found.
