Cutaneous sensory nerve-mediated microvascular vasodilation in normotensive and prehypertensive non-Hispanic Blacks and Whites

Relative to non-Hispanic Whites, non-Hispanic Blacks are disproportionately affected by elevated blood pressure (BP). It is unknown whether race or subclinical increases in BP affect the ability of cutaneous sensory nerves to induce cutaneous microvascular vasodilation. Sixteen participants who self-identified as non-Hispanic Black (n = 8) or non-Hispanic White (n = 8) were subgrouped as normotensive or prehypertensive. Participants were instrumented with three intradermal microdialysis fibers: (a) control, (b) 1 mu M sodium nitroprusside (SNP), an exogenous nitric oxide (NO) donor, and (c) 20 mM N-G-nitro-l-arginine methyl ester (L-NAME), a non-selective NO synthase inhibitor. A slow local heating protocol (33-40 degrees C, 0.1 degrees C/min) was used to assess the onset of cutaneous sensory nerve-mediated vasodilation (temperature threshold) and skin blood flow was measured using laser-Doppler flowmetry. At control sites, the temperature threshold occurred at a higher temperature in non-Hispanic Blacks (normotensive: 37.2 +/- 0.6 degrees C, prehypertensive: 38.9 +/- 0.5 degrees C) compared to non-Hispanic Whites (normotensive: 35.2 +/- 0.8 degrees C, prehypertensive: 35.2 +/- 0.9 degrees C). L-NAME shifted the temperature threshold higher in non-Hispanic Whites (normotensive: 37.8 +/- 0.7 degrees C, prehypertensive: 38.2 +/- 0.8 degrees C), but there was no observed effect in non-Hispanic Blacks. SNP did not affect temperature threshold in non-Hispanic Whites, but shifted the temperature threshold lower in non-Hispanic Blacks (normotensive: 34.6 +/- 1.2 degrees C, prehypertensive: 34.8 +/- 1.1 degrees C). SNP mitigated differences in temperature threshold across all groups. There was no effect found for BP status in either the non-Hispanic Black or non-Hispanic White groups. These data suggest that reduced NO bioavailability affects the ability of cutaneous sensory nerves to induce microvascular vasodilation in young, otherwise healthy non-Hispanic Blacks.