Baroreflex sensitivity is integral to blood pressure regulation, and varies among healthy, normotensive individuals. A reduced compensatory ability of baroreflex buffering in patients with carotid denervation results in blood pressure variability and an elevated blood pressure response to mental stress. Furthermore, 24-hour ambulatory blood pressure variability may also be a significant and independent risk determinant of cardiovascular disease. It remains unknown whether the degree of baroreflex sensitivity and ambulatory blood pressure variability are predictive of the pressor response to sympathoexcitatory stress in healthy humans. In this study the investigators propose a comprehensive evaluation of the relationships among the pressor and forearm vasodilator response to sympathoexcitation, ambulatory blood pressure variability, and baroreflex sensitivity in healthy normotensive subjects. Ultimately this study will provide preliminary data and protocol development for large-scale high resolution phenotyping in population-based trials aimed at determining the functional relevance of candidate gene variation in intermediate physiological traits pertinent to the pathogenesis of hypertension and cardiovascular disease.