Arterial baroreflex regulation of regional vascular conductance at rest and during exercise.

We tested the hypothesis that dynamic exercise resets the operating point and attenuates the spontaneous gain of the arterial baroreflex regulation of mesenteric and hindlimb vascular conductance in hypertensive rats. Eleven adult male spontaneously hypertensive rats were chronically instrumented with left carotid arterial catheters and Doppler ultrasonic flow probes around the superior mesenteric and left common iliac arteries. After the rats recovered, arterial baroreflex function was examined by recording reflex changes in conductance in response to spontaneous changes in mean arterial pressure before exercise and during steady-state treadmill running at 6 and 18 m/min. Dynamic exercise reduced the spontaneous baroreflex gain of mesenteric conductance (by 51 and 36%) and maximum mesenteric conductance (by 24 and 32%) at 6 and 18 m/min, respectively. In sharp contrast, dynamic exercise increased the spontaneous maximum iliac conductance (by 32 and 47%) without changing the spontaneous gain. Sinoaortic denervation eliminated the relationship between mean arterial pressure and conductance by reducing the mesenteric (92%) and iliac (68%) vascular conductance gain. These results demonstrate that dynamic exercise has differential effects on the regulation of mesenteric and iliac vascular conductance in hypertensive rats.