Baroreceptor modulation of active cutaneous vasodilation during dynamic exercise in humans.
The hypothesis that baroreceptor unloading during dynamic limits cutaneous vasodilation by withdrawal of active vasodilator activity was tested in seven human subjects. Increases in forearm skin blood flow (laser-Doppler velocimetry) at skin sites with (control) and without alpha-adrenergic vasoconstrictor activity (vasodilator only) and in arterial blood pressure (noninvasive) were measured and used to calculate cutaneous vascular conductance (CVC). Subjects performed two similar dynamic exercise (119 +/- 8 W) protocols with and without baroreceptor unloading induced by application of -40 mmHg lower body negative pressure (LBNP). The LBNP condition was reversed (i.e., either removed or applied) after 15 min while exercise continued for an additional 15 min. During exercise without LBNP, the increase in body core temperature (esophageal temperature) required to elicit active cutaneous vasodilation averaged 0.25 +/- 0.08 and 0.31 +/- 0.10 degrees C (SE) at control and vasodilator-only skin sites, respectively, and increased to 0.44 +/- 0.10 and 0.50 +/- 0.10 degrees C (P < 0.05 compared with without LBNP) during exercise with LBNP. During exercise baroreceptor unloading delayed the onset of cutaneous vasodilation and limited peak CVC at vasodilator-only skin sites. These data support the hypothesis that during exercise baroreceptor unloading modulates active cutaneous vasodilation.
John B. Pierce Laboratory and Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, Connecticut 06515, USA. mack@jbpierce.org
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D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D001833:Body Temperature Regulation / Q000187:drug effects; D001950:Bretylium Tosylate; D003080:Cold Temperature; D005080:Exercise Test; D005260:Female; D006801:Humans; D007478:Iontophoresis; D017078:Laser-Doppler Flowmetry; D008150:Lower Body Negative Pressure; D008297:Male; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012867:Skin / Q000098:blood supply* / Q000187:drug effects; D013546:Sweating; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D000317:Adrenergic alpha-Antagonists; D001950:Bretylium Tosylate