Control of ABP regulation in rats by interacting mechanisms: study by experiment, simulation, and time-frequency spectral analysis

Arterial blood pressure (ABP) variability spectra from sinoaortic deafferented (SAD) rats exhibit 10-100 times higher power at low frequencies (0.01-0.1 Hz) than in sham operated (SHAM) rats, and a prominent peak at the respiratory rate (1.7-2.0 Hz). SHAM rats exhibit a mid-frequency peak (0.3-0.5 Hz), and a small respiratory peak. The intact baroreflex in SHAM rats is thought to suppress the low frequency oscillations. Wigner-Ville (WV) spectra illustrate that following SAD, the slower mechanisms (e.g. renin-angiotensin system) that ordinarily play a minor role in regulation of ABP increase their gains over a period of weeks so that oscillations at their characteristic frequencies become pronounced. Furthermore temporal fluctuations in low frequency power seen in WV spectra apparently occur at the baroreflex frequency in SHAM and are abolished by SAD. To confirm these results, a simple ABP control model consisting of feedback and feedforward loops with appropriate gains and time constants was implemented. Consistent with the authors´ physiologic interpretation of the underlying processes, SAD simulation required that the gain of the lower frequency components be increased to obtain realistic data in time and frequency domains. Thus interaction between the baroreflex and lower frequency components is exposed