Neuroreport
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Axon reflex vasodilatation due to transcutaneous electrical stimulation in human skin was measured by laser Doppler imaging. Constant current pulses of 10 mA, 0.2 ms, delivered at 1 or 10 Hz for 2 min through a probe of 30 mm2 surface area did not induce a significant flare response, though this stimulus previously has been found supra-maximal for cutaneous polymodal (mechano-heat responsive) C-nociceptors in microneurography experiments. ⋯ This type of stimulus previously has been proven to recruit mechano-insensitive C-units in microneurography experiments, in contrast to stimuli from the 30 mm2 probe. It is concluded that mechano-insensitive C-nociceptors and not polymodal C-units mediate the axon reflex flare in human skin.