Figure 2.

Metabolic inhibition of α-adrenergic vasoconstriction in contracting skeletal muscle is prevented by NOS inhibition in wild type C57 mice. (a and c) Segments of an original record from an experiment in one C57 mouse showing the arterial blood pressure (BP) and femoral blood flow velocity (FBF) responses to intraarterial injection of norepinephrine (NE) in resting and contracting hindlimbs before and after NOS inhibition with l-NAME. Before l-NAME treatment, NE injection in resting hindlimbs increased arterial pressure and decreased femoral blood flow velocity (Left in a). In contrast, NE-mediated vasoconstriction was attenuated in contracting hindlimbs, as demonstrated by an increase, rather than decrease, in femoral blood flow velocity in response to NE (Right in a). In this same mouse, l-NAME treatment prevented the contraction-induced inhibition of adrenergic vasoconstriction as indicated by the decrease in femoral blood flow velocity in response to NE during hindlimb contraction (c). (b and d) Summary data showing the NE-mediated decreases in calculated femoral vascular conductance (FVC) in resting and contracting (Contr) hindlimb before and after l-NAME treatment. Hindlimb contraction greatly attenuated the NE-mediated decrease in vascular conductance before (b; n = 10), but not after (d; n = 8), l-NAME treatment.