Hypertension is the single most important contributing factor to both coronary heart disease and stroke, the two leading causes of death in the United States. Nonfatal and fatal cardiovascular diseases including coronary heart disease, ventricular arrhythmias and stroke, as well as renal disease and all-cause mortality increase progressively with higher levels of arterial pressure. In addition, both arterial and cardiopulmonary baroreflexes are less effective in controlling the circulation in hypertensive subjects. Cardiovascular mortality increases progressively with reduced baroreflex sensitivity. A limited number of studies performed with hypertensive subjects reported that endurance exercise training increased the sensitivity of the arterial baroreflex. An increased baroreflex gain may have cardioprotective effects and could be beneficial to patients at high risk for sudden cardiac death. A reduction in the incidence of sudden cardiac death among postinfarction patients participating in a multifactorial intervention program that included exercise has been reported. Therefore, this proposal is designed to determine the effect of endurance exercise training on the arterial and cardiopulmonary baroreflex regulation of the cardiovascular system in hypertensive rats. Specifically, the interaction of the arterial and cardiopulmonary baroreflex on the regulation of sympathetic nerve activity, regional blood flow, arterial pressure, heart rate and hormonal regulation (renin and arginine vasopressin) at rest and during exercise will be studied in sedentary and exercise trained hypertensive rats. The influence of peripheral (afferent activity) and central mechanisms in mediating the autonomic adaptations associated with exercise training will also be examined. These studies will provide a better understanding of the regulation of the neurohumoral drive to the circulation, the effect of exercise training on this regulation and the influence of central and peripheral mechanisms in mediating the autonomic adaptations associated with exercise training in hypertensive rats.
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