Fig. 1

Time series of carotid sinus pressure (CSP), sympathetic nerve activity (SNA), arterial pressure (AP), and heart rate (HR) obtained in one rat. In the left panels, stepwise CSP changes were repeated and referred to as S1 to S6. One minute after the completion of S2, low-dose (2 μg/kg) clonidine was intravenously administered. One minute after the completion of S4, high-dose (5 μg/kg) clonidine was intravenously administered. The baroreflex response in S2 was treated as the control, whereas the responses in S4 and S6 were used to evaluate the effects of low-dose and high-dose clonidine, respectively. In the right panels, hexamethonium bromide (C6) was intravenously administered. CSP was servo-controlled to mimic instantaneous AP during the C6 protocol. The CSP and AP signals are virtually the same at this time resolution. SNA was depicted as a 10-Hz resampled signal (gray) and a 2-s moving averaged signal (black). AP and HR were depicted as 200-Hz resampled signals (gray) and 2-s moving averaged signals (black)