Chronic absense of baroreceptor inputs prevents training-induced cardiovascular adjustments in normotensive and spontaneously hypertensive rats

Ceroni, Alexandre, et al. "Chronic absence of baroreceptor inputs prevents training‐induced cardiovascular adjustments in normotensive and spontaneously hypertensive rats." Experimental physiology 94.6 (2009): 630-640. It has been shown in both rats and humans, that a low intensity exercise regiment can be used to lower resting heart rate and consequentially blood pressure, in both normotensive and hypertensive individuals. Currently, cardiovascular responses during exercise are known to be driven by both a feedforward pathway (central command) and a feedback pathway (baroreceptors, chemoreceptors, muscle metaboreflex) that are synergistic in modifying cardiovascular responses. However, it is still unclear as to the underlying mechanisms during exercise drive the beneficial . Dr. Michelini's laboratory hypothesized that an intact baroreceptor reflex is necessary for training-induced adjustments of cardiovascular control to occur. To investigate their hypothesis they performed sino-aortic denervations in both normotensive (WKY) and spontaneously hypertensive rats (SHRs) and looked at the effects of low intensity exercising training in both sham WKYs and SHRs compared to SAD WKYs and SHRs. They found that a sino-aortic denervation completely blunted the affects of exercise training in both WKYs and SHRs compared to what was seen in both sham populations. More specifically, the SAD populations did not experience bradycardia or decreased blood pressure after a training as the sham groups (normotensive did not experience decreases in BP). They were however, able to observe reduce pressure variability and heart rate variability in SAD SHRs on an exercising regiment compared to the SAD SHRs not exercising. Overall, the study was able to show that the baroreceptor reflex input plays some role in allowing for cardiovascular adjustments driven by exercise training. ~JI