title: Which nerve fibers mediate the axon reflex flare in human skin?
abstract: 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. Pulses of the same strength from a pointed probe yielding a higher current density induced an extended and persistent flare. 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.
authors.affiliation: Department of Physiology and Experimental Pathophysiology, University of Erlangen-Nürnberg, Erlangen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Schmelz
authors.forename: K
authors.initials: K
authors.lastname: Michael
authors.forename: C
authors.initials: C
authors.lastname: Weidner
authors.forename: R
authors.initials: R
authors.lastname: Schmidt
authors.forename: H E
authors.initials: HE
authors.lastname: Torebjörk
authors.forename: H O
authors.initials: HO
authors.lastname: Handwerker
mesh_terms: D000328:Adult; D001369:Axons / Q000502:physiology*; D005260:Female; D006801:Humans; D017078:Laser-Doppler Flowmetry; D008297:Male; D008465:Mechanoreceptors / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology*; D009619:Nociceptors / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D012867:Skin / Q000098:blood supply* / Q000294:innervation*; D004561:Transcutaneous Electric Nerve Stimulation; D014664:Vasodilation