Traditionally, the standard deviation (SD) of the mean arterial pressure (AP) has been used as an index for the AP lability produced by interruption of baroreceptor afferents. Although a useful measure of variance about the mean, the SD does not provide any information about the temporal characteristics of this variability. We employed two different spectral analytic techniques to characterize AP waveforms in rats with sinoaortic deafferentation (SAD) and in sham-operated (Sham) rats to determine if the AP waveform in SAD animals was qualitatively and/or quantitatively different from that of Sham animals. The SAD and Sham animals exhibited qualitatively different spectral profiles, suggesting that lability of AP in SAD animals is not simply an exaggeration of normal fluctuations. In addition, a low-frequency (0.3-0.5 Hz) spectral peak was found in Sham but not SAD animals, suggesting that it is associated with the baroreflex. Finally, we observed in both normal rats and rats without intact baroreceptors that the spectral components of AP are not static but rather vary continuously across time.

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