title: Spreading of sudomotor axon reflexes in human skin.
abstract: BACKGROUND
  Acetylcholine (ACh) activates both sudomotor fibers and primary afferent nociceptors. This leads to sudomotor and vasodilator axon reflexes, which can be diminished, for example, in neuropathies. In some neuropathies, however, there is increased axon reflex sweating, a response pattern that has never been observed for vasodilator flares.
  
  
  OBJECTIVE
  To compare both types of axon reflexes and to elucidate possible differences.
  
  
  METHODS
  In healthy young male subjects, sweat response and flare reaction in response to ACh were quantified. Constant-current iontophoresis (300 mC) of ACh was performed on the lateral lower legs. The sudomotor axon reflex was visualized with iodine starch staining, and the sweat response was quantified with capacitance hygrometry (quantitative sudomotor axon reflex test [QSART]). The vasodilator flare was visualized and quantified by laser Doppler imaging. All measurements were performed during and for 10 minutes after finishing the iontophoresis.
  
  
  RESULTS
  The sudomotor axon reflex area increased from 30.6 cm2 at the end of the iontophoresis to 39.2 cm2 (p < 0.001) 10 minutes later, while QSART response had already decreased. Flare size and flare intensity remained nearly constant during the observation period.
  
  
  CONCLUSIONS
  Despite fast cleavage of acetylcholine by cholinesterases, sudomotor axon reflexes spread in the skin, indicating a possible peripheral amplification of sweating.
authors.affiliation: Department of Neurology, Johannes Gutenberg University, Mainz, Germany. schleret@uni-mainz.de
authors.forename: Tanja
authors.initials: T
authors.lastname: Schlereth
authors.forename: Nadine
authors.initials: N
authors.lastname: Brosda
authors.forename: Frank
authors.initials: F
authors.lastname: Birklein
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D001808:Blood Vessels / Q000294:innervation / Q000502:physiology; D004525:Efferent Pathways / Q000502:physiology; D006801:Humans; D008297:Male; D036421:Nerve Fibers, Unmyelinated / Q000502:physiology; D009619:Nociceptors / Q000502:physiology; D010525:Peripheral Nerves / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D011984:Sensory Receptor Cells / Q000502:physiology; D012867:Skin / Q000098:blood supply / Q000294:innervation*; D013545:Sweat Glands / Q000294:innervation* / Q000502:physiology*; D013546:Sweating / Q000502:physiology*; D017779:Sympathetic Fibers, Postganglionic / Q000502:physiology*; D014664:Vasodilation / Q000502:physiology; D014666:Vasomotor System / Q000502:physiology*
chemical_list: D000109:Acetylcholine