Exercise Training Increases Baroreceptor Gain Sensitivity in Normal and Hypertensive Rats

Exercise training attenuates arterial hypertension and increases baroreflex sensitivity in spontaneous hypertension. However, no information exists regarding the portion of the baroreflex arch in which this attenuation takes place. We tested the hypothesis that exercise training increases the afferent pathway sensitivity of baroreflex control in both normotensive and spontaneously hypertensive rats (SHR). Arterial pressure and whole-nerve activity of the aortic baroreceptor (multifiber preparation) were evaluated in 30 male rats assigned to 4 groups: sedentary and exercise-trained normotensive rats and sedentary and exercise-trained SHR. Exercise training was performed on a motor treadmill, 5 d/wk for 60 minutes, gradually progressing toward a speed of 26.8 m/min. Exercise training reduced mean arterial pressure in conscious exercise-trained SHR (183+/-4 versus 165+/-7 mm Hg). The relation between changes in aortic baroreceptor discharge and changes in systolic arterial pressure increased significantly in exercise-trained normotensive rats (2.09+/-0.1 versus 1.44+/-0.1%/mm Hg) and exercise-trained SHR (0.92+/-0.1 versus 0.71+/-0.1%/mm Hg) compared with their respective sedentary rats. Likewise, the average aortic baroreceptor gain sensitivity (calculated by logistic equation) was significantly higher in exercise-trained normotensive rats (2.25+/-0.19 versus 1.77+/-0.03%/mm Hg) and exercise-trained SHR (1.07+/-0.04 versus 0.82+/-0.05%/mm Hg) compared with their respective sedentary control rats. In conclusion, exercise training increases aortic baroreceptor gain sensitivity in normotensive and SHR, thus improving baroreceptor sensitivity, which may result in a more efficient arterial pressure regulation by the baroreflexes.