AJP - Heart and Circulatory Physiology, Vol 256, Issue 2 446-H454, Copyright © 1989 by American Physiological Society
Aberrant baroreceptor mechanotransduction in adult Dahl rats on low-salt diet
M. C. Andresen, S. K. Rudis and D. E. Bee
Department of Physiology and Biophysics, University of Texas Medical Branch, Galveston 77550.
Single fiber, regularly discharging baroreceptors (n = 118) from adult Dahl
salt-sensitive (DS) and salt-resistant (DR) rats on a low-salt diet were
studied using an in vitro aortic arch-aortic nerve preparation. Pressure
thresholds (Pth) and suprathreshold pressure sensitivities (Sth) were
determined from responses to slow ramps of pressure. Pressure-diameter
relationships measured in each rat were used to transform Pth and Sth
values to their mechanical equivalents in terms of aortic wall strain. DS
and DR ages were not different (approximately 50 wk). Despite the low-salt
diet, DS tail systolic blood pressures were significantly higher than DR by
approximately 25 mmHg. Pth averaged 84 mmHg in DR and 97 mmHg in DS. Sth
values were similar in DR and DS (average 1.44 and 1.39 spikes.s-1.mmHg-1
in DR and DS, respectively). Increased variance of baroreceptor properties
of DS over DR was a prominent finding and necessitated use of nonparametric
statistics. The cumulative distribution of Pth values of DS was
significantly different from DR, but Sth values were similar. Thus
baroreceptor pressure set points are altered in adult DS, but pressure
sensitivity per se is not. The differences in pressure parameters were not
eliminated by conversion to their mechanical equivalents. Correlation
analysis found only weak relationships between Pth and blood pressure for
DS and DR (r less than 0.40). Thus in contrast to previous studies in the
spontaneously hypertensive rat model, baroreceptors in adult DS on low salt
are characterized by elevated variability and a weaker than expected
correlation to the prevailing blood pressure in the animal.(ABSTRACT
TRUNCATED AT 250 WORDS)
