Differential Effects of Ca2+Channel Blockers Nifedipine and Cilnidipine on Arterial Elasticity in the Aortic and Femoral Arterial Segments of Anesthetized Rabbits

Ca2+ channel blockers have potent vasodilatory effects and excellent efficacy in preserving organ blood flow. These hemodynamic actions may be partly controlled by the functional stiffness of conduit arteries. In this study, we assessed the effects of the L-type Ca2+ channel blocker nifedipine on aortic and femoral arte-rial stiffness (referred to as aortic fl and femoral fl, respectively) in anesthetized rabbits. To further clarify the involvement of the autonomic nervous system, we compared the effects of nifedipine with those of the L/N-type Ca2+ channel blocker cilnidipine. Further, the effect of the a-adrenergic receptor blocker doxazo-sin on the effects of nifedipine on arterial elasticity was examined. An antihypertensive dose of nifedipine (300 mu g/kg, administered intravenously) was found to increase the aortic fl but hardly affected the femoral fl. An antihypertensive dose of cilnidipine (30 mu g/kg, administered intravenously) increased the aortic fl but de-creased the femoral fl. Interestingly, nifedipine decreased the femoral fl in the presence of the a-adrenoceptor blocker doxazosin (1 mg/kg, administered intravenously). These effects suggest that L-type Ca2+ channel blockers essentially increase vascular elasticity via the decrement in arterial stiffness in the femoral artery segment, which is modified by the presence or absence of the inhibitory effect of each drug on reflex sympa-thetic nerve activity, while decreasing vascular elasticity via the increment in arterial stiffness in the aortic segment independently of sympathetic nerve activity.