Using intradermal electrical stimulation to evaluate neurogenic control of skin blood flow

Abstract

Intradermal microdialysis and laser Doppler velocimetry were combined to evaluate neurogenic control of vasomotor activity of human skin blood vessels during non-painful intradermal electrical stimulation (E-stim). The laser Doppler flow probe was mounted directly over the microdialysis probe and the stimulating electrodes penetrated the skin 2 mm with the electrode tips separated by ≈ 4 mm. E-stim consisted of a constant current (1.8 ± 0.2 mA) pulses delivered at increasing frequency (0.2, 1, 2, 4, 8, and 32 Hz) in one minute steps. Stimulus- response curves of frequency versus skin blood flow (SkBF) were constructed and the area under the SkBF-time response curve was calculated. During saline perfusion increasing stimulus frequencies cause progressively greater reductions in SkBF with significant declines from baseline observed at frequencies of ≥2 Hz (p<0.05). The peak reduction in SkBF at 32 Hz was represented by an AUC of −2566 ± 854 SkBF·sec. In contrast, following adrenergic blockade (phentolamine (0.05 mg/ml), propranolol (1 mM), and BIBP-3226 (10 μM) SkBF failed to decline below baseline and the AUC at 32 Hz averaged only −342 ± 540 SkBF·sec (p<0.05). These data support the hypothesis that non-painful E-stim protocol provided a significant activation of the local sympathetic vasoconstrictor nerves and may provide a novel approach to investigating active cutaneous vasodilation.