title: Thermal grill-evoked sensations of heat correlate with cold pain threshold and are enhanced by menthol and cinnamaldehyde.
abstract: BACKGROUND
  Thunberg's thermal grill produces a sensation of strong heat upon skin contact with spatially interlaced innocuous warm and cool stimuli.
  
  
  METHODS
  To examine the classes of peripheral axons that might contribute to this illusion, the effects of topical l-menthol, an activator of TRPM8, and cinnamaldehyde, a TRPA1 agonist, on the magnitude of thermal sensations were examined during grill stimulation in healthy volunteers.
  
  
  RESULTS
  Under control conditions, cutaneous grill stimulation (interlaced 20/40 °C) evoked a sensation of heat, and for individual subjects, the magnitude of this heat sensation was positively correlated with cold pain threshold (CPT). Menthol increased the CPT and enhanced the magnitude of grill-evoked heat. Cinnamaldehyde intensified warm sensations, reduced heat pain threshold and also enhanced grill-evoked heat.
  
  
  CONCLUSIONS
  Both TRPM8-expressing and TRPA1-expressing afferent axons can affect grill-evoked thermal sensations. The enhancement of grill-evoked sensations of temperature with menthol and cinnamaldehyde may provide an additional clinically relevant means of testing altered thermal sensitivity, which is often affected in neuropathic patient groups.
authors.affiliation: Department of Physiology, University of Munich, Germany. beate.averbeck@lrz.uni-muenchen.de
authors.forename: B
authors.initials: B
authors.lastname: Averbeck
authors.forename: F
authors.initials: F
authors.lastname: Rucker
authors.forename: R P
authors.initials: RP
authors.lastname: Laubender
authors.forename: R W
authors.initials: RW
authors.lastname: Carr
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives* / Q000494:pharmacology; D000328:Adult; D003080:Cold Temperature; D005260:Female; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008610:Menthol / Q000494:pharmacology*; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D010146:Pain / Q000503:physiopathology* / Q000517:prevention & control; D010147:Pain Measurement / Q000379:methods; D017288:Pain Threshold / Q000187:drug effects* / Q000502:physiology; D012867:Skin / Q000187:drug effects*; D013697:Thermosensing / Q000187:drug effects / Q000502:physiology
chemical_list: D008610:Menthol; D000171:Acrolein; C012843:cinnamaldehyde