Abstract
In summary, the relative roles of the parasympathetic and sympathetic nervous systems in baroreceptor reflex heart rate control have been studied in eleven normal young men. These data have been compared to the results of similar studies in a heart transplant subject. The findings indicate that in normal conscious men, reflex parasympathetic stimulation and withdrawal primarily control heart rate responses to changes in blood pressure. Beta-adrenergic activity, while influencing basal heart rate plays little, if any, role in baroreceptor reflex heart rate control. The Valsalva maneuver may be used as an effective measure of parasympathetic integrity but it may not be used as a reliable index of sympathetic integrity. The pharmacologically denervated heart is similar in terms of reflex responses to the surgically denervated heart in conscious man. The heart rate responses to Valsalva maneuver, amyl nitrite inhalation, and phenylephrine infusion should be reliable indices of parasympathetic reinnervation of the transplanted heart should reinnervation occur.
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