Frequency components of systolic blood pressure variability reflect vasomotor and cardiac sympathetic functions in conscious rats

In this study, after confirming the suppression of autonomic nervous function by isoflurane anesthesia using autonomic antagonists, we pharmacologically investigated the involvement of vasomotor and cardiac sympathetic functions in systolic blood pressure variability (SBPV) frequency components in conscious rats at rest and during exposure to low-ambient temperature (LT-exposure, 9°C for 90 min). Under unanesthesia, phentolamine administration (α-adrenoceptor antagonist, 10 mg/kg) decreased the mid-frequency component (MF 0.33-0.73 Hz) and inversely increased the high-frequency component (HF 1.3-2.5 Hz). The increased HF was suppressed by subsequent treatment with atenolol (β-adrenoceptor antagonist, 10 mg/kg), but not with atropine (muscarinic receptor antagonist, 10 mg/kg). Moreover, phentolamine administration after atenolol decreased MF, but did not increase HF. LT-exposure increased MF and HF; however, phentolamine pretreatment suppressed the increased MF during LT-exposure, and atenolol pretreatment dose-dependently decreased the increased HF. These results suggest that MF and HF of SBPV may reflect α-adrenoceptor-mediated vasomotor function and β-adrenoceptor-mediated cardiac sympathetic function, respectively, in the conscious state.