Effect of systemic α1-adrenergic receptor blockade on central blood pressure response during exercise

The aortic pulse pressure (PP), which consists mainly of the incident wave and the reflected wave, has emerged as an important property of systemic blood vessels underlying the pathophysiology of cardiovascular disease. To determine the role of sympathetic nerve activity on the aortic PP response during dynamic exercise, we evaluated aortic hemodynamics during the right-leg knee-extension (40 and 60 % of maximal voluntary contraction) in six young adults with and without the systemic alpha 1-adrenergic receptor blockade using prazosin (1 mg/20 kg body weight). The use of prazosin attenuated the exercise-induced increase in aortic PP (P < 0.05) but not in radial arterial PP. The amplitude of the reflected waves (via augmentation index) significantly decreased with the exercise and decreased more with the use of prazosin. These results suggest that during dynamic exercise the alpha 1-adrenergic-mediated vasoconstrictor tone of the peripheral resistance vessels is manifestly involved in the magnitude of the reflected wave and the modulation of the aortic PP responses.