AJP - Regulatory, Integrative and Comparative Physiology, Vol 266, Issue 1 27-R39, Copyright © 1994 by American Physiological Society
Reflex regulation of renal nerve activity in cardiac failure
G. F. DiBona and L. L. Sawin
Department of Internal Medicine, University of Iowa College of Medicine, Iowa City.
Efferent renal sympathetic nerve activity (ERSNA) is increased in the rat
with low-cardiac-output congestive heart failure (CHF; myocardial
infarction). Arterial and cardiopulmonary baroreflex control of ERSNA in
CHF and control rats was examined. Cardiac index and arterial pressure were
lower and total peripheral resistance index, left ventricular end-diastolic
pressure, and heart-to-body weight ratio were higher in CHF than in control
rats. Increases in left ventricular end diastolic pressure produced by
intravenous volume loading failed to increase cardiac index in CHF rats as
it did in control rats. Single-unit analysis of aortic baroreceptor nerve
activity showed that CHF rats had higher pressure threshold, lower
frequency at pressure threshold, and lower gain than control rats. Arterial
baroreflex control of ERSNA was attenuated; this was due to diminished gain
of the afferent limb while the gain of the central portion of the reflex
was normal. Single-unit analysis of vagal nerve activity showed that CHF
rats had higher pressure threshold, lower frequency at saturation, and
lower gain than control rats. Cardiopulmonary baroreflex control of ERSNA
was attenuated; this was due to diminished gain of the afferent limb while
the gain of the central portion of the reflex was normal. In the CHF rat,
arterial and cardiopulmonary baroreflex control of ERSNA is markedly
attenuated because of abnormalities in the periphery at the level of the
aortic and cardiopulmonary receptors, respectively, and not in the central
nervous system.
