Figure 2. Dose-dependent depression of the baroreceptor reflex-mediated bradycardia induced by NTS microinjections of ANGII.

In the WHBP, the baroreceptor reflex was stimulated by increasing perfusion pressure. Pressure ramps generated were within the linear part of the baroreceptor reflex sensitivity curve. Note that the values for the rate of rise of the pressure ramp (dP/dt) are comparable. Microinjection of ANGII produced a dose-dependent suppression of the reflex bradycardia (P < 0·01) whereas phrenic nerve activity responses were not affected significantly. The ANGII-induced depression of the baroreceptor-evoked bradycardia was mediated by AT₁ receptors since it could be reversed by addition of losartan to the perfusate. Abbreviations as in Fig. 1.