Adult obese Zucker rats (OZR) have elevated sympathetic vasomotor tone and arterial pressure (AP) with blunted baroreflex-mediated changes in heart rate (HR) compared to adult lean Zucker rats (LZR). The present study examined whether compromised cardiac baroreflexes are indicative of attenuated sympathetic responses. In addition, because juvenile OZR have a normal mean AP, we determined whether baroreflexes are fully functional prior to hypertension. At 13 wks adult OZR had an elevated baseline mean AP compared to LZR (137+/-3 vs. 123+/-5 mmHg, P <0.05) under urethane anesthesia. Phenylephrine-induced increases in AP evoked smaller inhibitions of splanchnic sympathetic nerve activity (SNA) and HR in OZR compared to LZR. In addition, sympatho-excitatory responses to nitroprusside-induced hypotension were also blunted in OZR. Sigmoid analysis revealed a decreased gain, a higher mean AP50, and reduced range of changes in SNA in OZR. In contrast, at 7 wks of age although juvenile OZR weighed more than LZR (313+/-13 vs. 204+/-4 g, P < 0.05), mean AP was comparable in both groups (122+/-5 vs. 121+/-4, N.S.). In these rats rapid changes in AP evoked comparable changes in SNA and HR in OZR and LZR. Sigmoid analysis revealed that although the gain of the reflex was blunted in the OZR (P<0.05), the mean AP50 and range of changes in SNA were comparable in OZR and LZR. Together these data indicate that in adult OZR sympathetic responses to acute changes in AP are smaller than those observed in adult LZR, and that impairment of baroreceptor reflexes in OZR is not limited to regulation of HR, but extends to sympathetic vasomotor control. In addition, most of these deficits in baroreflex control of SNA develop in adulthood long after the onset of obesity and when other deficits in cardiovascular regulation are present.