• B Averbeck, F Rucker, R P Laubender, and R W Carr.
• Department of Physiology, University of Munich, Germany. beate.averbeck@lrz.uni-muenchen.de
• Eur J Pain. 2013 May 1; 17 (5): 724-34.

BackgroundThunberg's thermal grill produces a sensation of strong heat upon skin contact with spatially interlaced innocuous warm and cool stimuli.MethodsTo 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.ResultsUnder 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.ConclusionsBoth 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.© 2012 European Federation of International Association for the Study of Pain Chapters.

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