Quantitative relationship between fluctuations of blood pressure and sympathetic nerve activity in pentobarbital anesthetized rats

Transfer function analysis was used to examine the coupling between the sym pathetic nerve activity (SNA) and the blood pressure (BP) fluctuations. In pentobarbital anesthetized Wistar rats, linear regression of the relationsh ip between frequency (X-axis) and the logarithmic transfer magnitude, i.e, log (BP power density/renal SNA power density) (Y-axis), in the low frequen cy range (0.016-0.85 Hz) revealed an excellent fit (r = 0.97-0.98). Compari ng the regression lines, rats under large dose of pentobarbital anesthesia (40 mg/kg, i.v. single dose) had significantly smaller intercept and slope Values compared to rats under small dose of pentobarbital anesthesia (12.5 mg/kg). When intercept and slope values were compared between intact and ac utely sinoaortic denervated rats, no significant difference were found. The results suggest that sympathetic modulation of vasomotor tone may be a maj or factor in generating BP fluctuations between 0.016 and 0.85 Hz in rats. Furthermore, these results support the possibility of using low frequency s pectral power of BP to quantitatively estimate the fluctuations of SNA for rats under pentobarbital anesthesia if anesthetic depth is controlled. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.