The influence of topical capsaicin on the local thermal control of skin blood flow in humans

1 The University of Texas Health Science Center, Department of Physiology, San Antonio 78229; 2 Texas Lutheran University, Seguin, Texas 78155; and 3 Laboratoire de Physiologie et d'Explorations Vasculaires, Centre Hospitalier Universitaire d'Angers, 49045 Angers Cedex 01, France To test whether heat-sensitive receptors participate in the cutaneous vascular responses to direct heating, we monitored skin blood flow (SkBF; laser Doppler flowmetry) where the sensation of heat was induced either by local warming (T Loc ; Peltier cooling/heating unit) or by both direct warming and chemical stimulation of heat-sensitive nociceptors (capsaicin). In part I , topical capsaicin (0.075 or 0.025%) was applied to 12 cm 2 of skin 1 h before stepwise local warming of untreated and capsaicin-treated forearm skin. Pretreatment with 0.075% capsaicin cream shifted the SkBF/T Loc relationship to lower temperatures by an average of 6 ± 0.8°C ( P