Contribution of sensory nerves to cutaneous reactive hyperaemia in non-Hispanic Black and White young adults

Abstract

New findings: What is the central question of this study? Does cutaneous sensory nerve-mediated vasodilatation differ between non-Hispanic Black and White young adults? What is the main finding and its importance? The magnitude of cutaneous reactive hyperaemia is lower in non-Hispanic Black relative to non-Hispanic White young adults, but the overall sensory nerve contribution is the same, suggesting that sensory nerve function is similar in both non-Hispanic Black and White young adults.

Abstract: The aim of this study was to assess cutaneous sensory nerve function, independent of nitric oxide, in non-Hispanic Black and White young adults. We tested the hypothesis that cutaneous reactive hyperaemia and sensory nerve-mediated vasodilatation would be lower in non-Hispanic Black young adults relative to non-Hispanic White young adults. Twenty-four participants who self-identified as non-Hispanic Black (n = 12) or non-Hispanic White (n = 12) were recruited. All participants underwent three bouts of reactive hyperaemia. An index of skin blood flow was measured continuously using laser-Doppler flowmetry at a control site and at a site treated with topical 4% lignocaine to inhibit sensory nerve function. Peak reactive hyperaemia was lower in non-Hispanic Black relative to non-Hispanic White participants (P < 0.001). Total reactive hyperaemia was lower in non-Hispanic Black [mean (SD); control, 4085 (955)%CVC_max s; lignocaine, 2127 (639) percent maximal cutaneous vascular conductance * seconds, %CVC_max s] relative to non-Hispanic White [control: 6820 (1179)%CVC_max s; lignocaine, 3573 (712)%CVC_max s] participants (P < 0.001 for both sites). There was no difference between groups for the calculated contribution of sensory nerves to either the peak [non-Hispanic Black, 25 (14)%; non-Hispanic White, 19 (13)%] or total reactive hyperaemic response [non-Hispanic Black, 48 (10)%; non-Hispanic White, 47 (10)%]. These data suggest that cutaneous reactive hyperaemia is lower in non-Hispanic Black young adults, but the sensory nerve contribution is similar in non-Hispanic Black and White young adults.

Keywords: arterial occlusion; human; microvascular function.

FIGURE 1

Peak reactive hyperaemia. (a) Peak reactive hyperaemia in non‐Hispanic Black (n = 12; six women and six men) and White (n = 12; seven women and five men) participants at control (circles) and lignocaine (triangles) sites. Filled symbols are data from women; open symbols are data from men. ^* P < 0.001 control versus non‐Hispanic White participants. ^# P < 0.001 lignocaine versus respective control sites. Data were analysed via two‐way ANOVA. (b) Calculated percentage sensory nerve contribution to peak reactive hyperaemia in non‐Hispanic Black (squares) and non‐Hispanic White (diamonds) young adults. There was no difference in percentage sensory nerve contribution between groups. Data were analysed by Student's unpaired t‐test.

FIGURE 2

Total reactive hyperaemic response. (a) Total reactive hyperaemia in non‐Hispanic Black (n = 12; six women and six men) and White (n = 12; seven women and five men) participants at control (circles) and lignocaine (triangles) sites. Filled symbols are data from women; open symbols are data from men. ^* P < 0.001 both control and lignocaine sites versus non‐Hispanic White participants. ^# P < 0.001 lignocaine versus respective control sites. Data were analysed via two‐way ANOVA. (b) Calculated percentage sensory nerve contribution to total reactive hyperaemia in non‐Hispanic Black (squares) and non‐Hispanic White (diamonds) young adults. There was no difference in percentage sensory nerve contribution between groups. Data were analysed by Student's unpaired t‐test.