REDUCED VASCULAR RESPONSIVENESS AFTER A SINGLE BOUT OF DYNAMIC EXERCISE IN THE CONSCIOUS RABBIT

We measured agonist-induced changes in iliac artery blood flow velocity (IFV) independent of baroreflex-mediated compensatory mechanisms in chronically instrumented New Zealand White rabbits (n = 8). Animals were instrumented with a Doppler flow probe around the right common iliac artery. A Teflon catheter was inserted into the right iliolumbar artery for local infusion of the vasoactive agonists. Another Teflon catheter was inserted in the left femoral artery for the measurement of pulsatile and mean arterial (MAP) blood pressures and heart rate (HR). The alpha-adrenergic receptor agonist phenylephrine (PE, 1.32-10.0 mug), the beta1- and beta2-adrenergic receptor agonist isoproterenol (IP, 0.022-0.11 mug), and the purinergic receptor agonist adenosine (AD, 10.0-100.0 mug) were injected into the functionally isolated hindlimb, and dose-response curves were generated. Changes in IFV were obtained without changes in MAP or HR. Exercise increased HR, MAP, and IFV (65.3 +/- 7.1 beats/min, 11.1 +/- 2.2 mmHg, and 2.2 +/- 0.3 kHz, respectively). The maximum responses to PE, AD, and IP were reduced 29.0 +/- 6.7, 50.7 +/- 8.5, and 61.0 +/- 8.1%, respectively, after exercise. In conclusion, exercise attenuated adrenergic and purinergic receptor-mediated vascular responses in the intact conscious rabbit.