Regional differences in noradrenergic and nitric oxide involvement in the cutaneous vasodilator responses to local heating

Abstract

We investigated the roles of nitric oxide synthase (NOS) and sympathetic nerves in regional cutaneous vasodilator responses to a localized heating stimulus. In a three‐part study, forearm and lower‐leg sites were instrumented with microdialysis fibers, local skin heaters, and laser‐Doppler probes. In Part 1, we tested a heat‐reheat protocol: skin sites were heated from 33 to 42 °C, cooled to 33 °C for 1 h, and reheated again to 42 °C. Baseline, initial peak, and secondary plateau vasodilator responses were compared; there were no differences (P>0.05) within (bouts of heating) or between sites (arms vs. legs). In Part 2, L‐NAME was used to inhibit NOS activity. L‐NAME treatment resulted in a reduction (P<0.05) in both the axon reflex and secondary plateau when compared to the untreated control responses in both arms and legs. In Part 3, we tested the role of sympathetic nerves in response to local heating using bretylium tosylate (BT). BT treatment resulted in a reduction (P<0.05) in both the axon reflex and secondary plateau when compared to control in both arms and legs. These data indicate that cutaneous vasodilator mechanisms are similar between arm and leg skin. Supported by Univ. of Alabama.