Fig. 2.

Percent change in experimental limb iliac vascular conductance in response to intra-arterial infusion of the selective α1-adrenergic receptor antagonist prazosin (0.25 μg·ml⁻¹·min⁻¹) at rest and during treadmill running at 2.5 mph and 4 mph with 2.5% grade in young (open bars) and old (black bars) beagles. Absolute values for all hemodynamic variables prior to and following antagonist infusion are presented in Table 2. Values are expressed as means ± SE. ‡P < 0.001 indicates a main effect of exercise intensity.