Nonstationary fluctuations of arterial pressure in sino-aortic deafferented rats

Sinaortic deafferented (SAD) rats, in which the baroreflex is removed, exhibit increased fluctuations in arterial pressure (AP) compared to sham-operated (SHM) rats. The power spectrum of AP variability is estimated using the method of averaged periodograms. The relatively short interval over which the AP time series is stationary prevents resolution of spectral components below 1 Hz by this method. An autoregressive (AR) model is used, allowing resolution of spectral peaks at frequencies below 1 Hz. Choice of model order was guided by the Akaike information criterion. A peak at 0.4 Hz was found in the SHM but not the SAD rats, suggesting that it may represent oscillations associated with neural and/or humoral component of the baroflex. A smaller peak near 2 Hz is thought to represent respiratory influences on AP.<>