Exercise Training Increases Baroreceptor Gain Sensitivity in Normal and Hypertensive Rats

Abstract

Abstract-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 (183Ϯ4 versus 165Ϯ7 mm Hg). The relation between changes in aortic baroreceptor discharge and changes in systolic arterial pressure increased significantly in exercise-trained normotensive rats (2.09Ϯ0.1 versus 1.44Ϯ0.1%/mm Hg) and exercise-trained SHR (0.92Ϯ0.1 versus 0.71Ϯ0.1%/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 (2.25Ϯ0.19 versus 1.77Ϯ0.03%/mm Hg) and exercise-trained SHR (1.07Ϯ0.04 versus 0.82Ϯ0.05%/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.

The effect of 4 weeks of aerobic exercise on vascular and baroreflex function of young men with a family history of hypertension

“…35 Animal studies, however, have shown that both acute and chronic exercise did improve baroreflex sensitivity in both normal and hypertensive rats. 36,37 In the present study, CPBR control of forearm vascular resistance did not significantly improve following 4 weeks of cycle exercise. A possible explanation for this lack of change could be the short duration of the exercise program.…”

Tonic and reflex cardiovascular autonomic control in trained-female rats

“…Whereas baseline AP is unaltered after training, the controlling mechanisms are changed. There is evidence supporting the increase in baroreflex gain in trained subjects (6,7,(9)(10)(11)23,29). Exercise training of normotensive male rats enhanced hypotension-induced tachycardia, whereas the bradycardic response was decreased or unchanged (7,23).…”

“…In contrast, resting bradycardia in young trained male rats has been more closely associated with alterations in cardiac pacemakers (4,5). Moreover, improvement in baroreflex control of HR observed in trained male animals (6)(7)(8) and humans (9)(10)(11) may also play a role in basal HR changes. Additionally, few studies have so far analyzed the effects of exercise training on cardiopulmonary reflex, which plays a role in the homeostasis of fluid balance.…”

Effect of exercise on the maternal outcome in pregnancy of spontaneously hypertensive rats

“…* p<0.05 -significant statistically difference as compared to SHR Control group is associated with beneficial effects on BP, neurohumoral release and autonomic activity. However, among the antihypertensive mechanisms of exercise that remain uncertain are the increased vascular bed 38 , increased sensitivity of the baroreceptors 39 , increased formation and action of antioxidants 40 and also the modulation of sympathetic and parasympathetic tone 41 .…”