AJP - Heart and Circulatory Physiology, Vol 253, Issue 1 176-H183, Copyright © 1987 by American Physiological Society
Hemodynamic regulation in SHR: investigation by spectral analysis
S. Akselrod, S. Eliash, O. Oz and S. Cohen
This work is based on the premise that hypertension in the spontaneously
hypertensive rat (SHR) is a consequence of an imbalance in autonomic
cardiovascular control. Spontaneous, instantaneous fluctuations in heart
rate (HR) and arterial blood pressure (ABP) were studied by spectral
analysis in age-matched groups of SHR and normotensive Wistar-Kyoto (WKY)
rats. Continuous recordings of ABP and HR made in conscious, unrestrained,
young 1-, 2-, 3-, and 6-mo-old rats show that power spectra of HR
fluctuations were similar in both strains, whereas ABP fluctuations were
significantly different in the low, presumably vasomotor frequency range
being reduced in SHR as compared with age-matched WKY rats. In 1-mo-old
rats, the difference between strains became smaller with urethan anesthesia
and disappeared with spinalization, suggesting that it might have
originated in some disparity between the strains at the level of the
central nervous system. Low doses of phentolamine elicited a fall in
low-frequency ABP fluctuations of WKY but a rise in SHR, whereas larger
doses produced a fall in the power of both. In SHR, reduction in the power
spectrum of ABP fluctuations in the presence of unaltered HR fluctuations
may indicate an impaired control of sympathetic drive to resistance vessels
compared with WKY. Note that in young SHR, hypertension also cannot be
detected by conventional measurement. Fluctuations in ABP in WKY may
reflect an optimal level of sympathetic activity; reduction in fluctuations
may be associated with an increase or decrease in sympathetic activity at
the vascular bed.(ABSTRACT TRUNCATED AT 250 WORDS)
