Impaired autonomic nervous activity in the gene targeted mice assessed by power spectra of heart rate and arterial blood pressure variabilities

The aim of this study was to analyze autonomic nervous activity by using autoregressive (AR) power spectral analysis in mice lacking ryanodine receptor type 3 (RyR-3) generated by the gene targeting technique. Cardiac sympathetic and parasympathetic, vasomotor sympathetic activities were assessed on the basis of the power spectra for heart rate variability (HRV) and systolic blood pressure variability (SPV) calculated by AR spectral analysis based on the Burg's maximum entropy method. In RyR-3 knockout mice, the low frequency power of HRV (LF-HRV, 0.1-1.0 Hz band), the high frequency power of HRV (HF-HRV, 1.0-5.0 Hz band) and the LF/HF ratio representing cardiac sympathetic activity or sympatho-vagal balance, respectively were significantly smaller than in wild-type mice. Additionally, the low frequency component of SPV (LF-SPV) showing vasomotor sympathetic activity was significantly smaller in RyR-3 than wild-type mice. These results support the view that insufficient sympathetic control of HR and blood pressure and altered sympatho-vagal balance underlies reduction of HRV and SPV in RyR-3 knockout mice. In conclusion, by analyzing AR power spectra of HRV and SPV, we suggest that cardiac sympathetic and parasympathetic activities as well as vasomotor sympathetic tone are smaller in RyR-3 knockout mice as compared with wild-type mice, and mice lacking RyR-3 show an impairment to the physiological autonomic control of cardiovascular system.