|
|
||||||||
1 Department of Physiology and Biophysics, University of Nebraska College of Medicine, Omaha, Nebraska 68198; and 2 University of Texas Health Sciences Center at San Antonio, San Antonio, Texas 78284
Blockade of the angiotensin II (ANG II) type 1 receptor (AT1) has been shown to
restore baroreflex sensitivity in rats and rabbits with experimental
chronic heart failure (CHF). Because the modulation of baroreflex
function in response to ANG II is mediated in part by
AT1 receptors located in the area
postrema, we hypothesized that lesions of the area postrema would
prevent the enhancement in baroreflex function in response to
AT1-receptor blockade in rabbits
with pacing-induced CHF. Experiments were carried out on 24 male New
Zealand White rabbits that were divided into sham
(n = 12) and lesioned
(n = 12) groups further divided into
normal and CHF subgroups (n = 6 each).
All rabbits were identically instrumented to measure cardiac external
dimensions, central venous pressure, arterial pressure, heart rate
(HR), and renal sympathetic nerve activity (RSNA). After 3-4 wk of
pacing, baroreflex sensitivity (infusions of phenylephrine and
nitroprusside) was evaluated before and after intravenous
administration of the AT1-receptor
antagonist L-158,809. Maximum baroreflex sensitivity in nonpaced
rabbits was 5.4 ± 0.7 beats · min
1 · mmHg
1
and 5.2 ± 0.5% of maximum/mmHg for HR and RSNA curves,
respectively, and was not altered by L-158,809 in either intact or
lesioned rabbits. In contrast, L-158,809 enhanced baroreflex
sensitivity in intact rabbits with CHF (HR from 1.6 ± 0.3 to 4.1 ± 0.7 beats · min
1 · mmHg
1,
P < 0.001; RSNA from 2.3 ± 0.2 to 4.9 ± 0.4% of maximum/mmHg, P < 0.001). However, in CHF rabbits
with area postrema lesions, L-158,809 failed to enhance baroreflex
sensitivity. Interestingly, area postrema lesions did not normalize the
baroreflex in CHF rabbits. From these data we conclude that the area
postrema mediates the normalization of baroreflex sensitivity after
AT1 blockade in rabbits with CHF
but does not modify resting baroreflex function.
angiotensin II; angiotensin receptors; experimental heart failure; central nervous system; sympathetic nerve activity
This article has been cited by other articles:
![]() |
G.-Q. Zhu, Y. Xu, L.-M. Zhou, Y.-H. Li, L.-M. Fan, W. Wang, X.-Y. Gao, and Q. Chen Enhanced cardiac sympathetic afferent reflex involved in sympathetic overactivity in renovascular hypertensive rats Exp Physiol, July 1, 2009; 94(7): 785 - 794. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. M. Mousa, D. Liu, K. G. Cornish, and I. H. Zucker Exercise training enhances baroreflex sensitivity by an angiotensin II-dependent mechanism in chronic heart failure J Appl Physiol, March 1, 2008; 104(3): 616 - 624. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. S. P. Tan, S. Killinger, J. Horiuchi, and R. A. L. Dampney Baroreceptor reflex modulation by circulating angiotensin II is mediated by AT1 receptors in the nucleus tractus solitarius Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2007; 293(6): R2267 - R2278. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. L. Daubert, D. Liu, I. H. Zucker, and V. L. Brooks Roles of nitric oxide and angiotensin II in the impaired baroreflex gain of pregnancy Am J Physiol Regulatory Integrative Comp Physiol, June 1, 2007; 292(6): R2179 - R2187. [Abstract] [Full Text] [PDF] |
||||
![]() |
L. Gao, Z. Zhu, I. H. Zucker, and W. Wang Cardiac sympathetic afferent stimulation impairs baroreflex control of renal sympathetic nerve activity in rats Am J Physiol Heart Circ Physiol, May 1, 2004; 286(5): H1706 - H1711. [Abstract] [Full Text] [PDF] |
||||
![]() |
K. P. O'Hagan, K. A. Skogg, and J. B. Stevenson AT1 receptor block does not affect arterial baroreflex during pregnancy in rabbits Am J Physiol Heart Circ Physiol, May 1, 2001; 280(5): H1996 - H2005. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Kawai, S. Y. Stevens, and C.-S. Liang Renin-angiotensin system inhibition on noradrenergic nerve terminal function in pacing-induced heart failure Am J Physiol Heart Circ Physiol, December 1, 2000; 279(6): H3012 - H3019. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. Shite, E. Dong, H. Kawai, S. Y. Stevens, and C.-S. Liang Selegiline improves cardiac sympathetic terminal function and beta -adrenergic responsiveness in heart failure Am J Physiol Heart Circ Physiol, September 1, 2000; 279(3): H1283 - H1290. [Abstract] [Full Text] [PDF] |
||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |