Brain angiotensin ii tonically modulates the sympathetic baroreflex
in the rabbit ventrolateral medulla.
Saigusa, Takeshi, Masami Iriki, and Jun Arita.
Department of Physiology, Yamanashi Medical University, Tamaho,
Nakakoma, Yamanashi 409-38, JAPAN
APStracts 3:0121H, 1996.
The role of endogenous angiotensin?II (ANG?II) at the level of the
rostral and caudal ventrolateral medulla (RVLM and CVLM) in the
control of sympathetic baroreflex function was investigated in
urethane anesthetized rabbits. The baroreflex relationship between
mean arterial pressure (MAP) and integrated renal sympathetic nerve
activity (RSNA) was compared before and during a microinfusion of
saralasin, an ANG?II receptor antagonist, into RVLM or CVLM. The
infusion of saralasin (20?pmol/min) into RVLM reduced the upper
plateau, the range and the range-dependent gain of the baroreflex, as
well as the resting level of RSNA. The infusion of saralasin into
CVLM augmented the upper plateau, the reflex range and the range
-dependent gain, while it did not alter the resting level of RSNA or
MAP. These results suggest that 1) the ANG?II networks in RVLM are
tonically active, which influence the resting level of the
sympathetic outflow, and also facilitate the sympathetic baroreflex
function; and that 2) the ANG?II networks in CVLM do not
significantly influence the sympathetic activity in resting state,
but exert an inhibitory effect on the baroreflex response at the time
when arterial pressure decreases below the resting level.
Received 10 October 1995; accepted in final form 7 March 1996.
APS Manuscript Number H945-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96