Central effect of angiotensin II on baroreflex regulation in conscious rabbits
Matsumura, Y.; Hasser, E.M.; Bishop, V.S.
American Journal of Physiology 256(3 Pt 2): R694-R700
1989
ISSN/ISBN: 0002-9513 PMID: 2923258 Document Number: 342224
Central effects of angiotensin II (ANG II) on arterial baroreflex control of renal sympathetic nerve activity (RSNA) and heart rate (HR) were examined in conscious rabbits. Intravenous infusion of ANG II (5-320 ng .cntdot. kg-1 .cntdot. min-1) significantly reduced the baroreflex inhibition of HR compared with phenylephrine (PE) (0.5-16 .mu.g .cntdot. kg-1 .cntdot. min-1), whereas reflex inhibition of RSNA was unaltered. Background intravenous infusions of ANG II did not alter the baroreflex responses of RSNA nro HR to increases (with PE) or decreases in mean arterial pressure (with nitroglycerin or inferior vena cava occluder). When ANG II was infused into the vertebral artery (VA) the integrated pressor response was greater than intravenous infusions. Progressive VA infusions of ANG II resulted in a significantly blunted baroreflex inhibition of HR compared with intravenous infusions, whereas the reflex inhibition of RSNA was identical between VA and intravenous infusions. These results suggests that ANG II produces central pressor effects via a hindbrain site and reduces baroreflex inhibition of HR without altering baroreflex inhibition of RSNA.