Referenced in: none

Automatically associated channels: Kv7.2 , TRP , TRPM , TRPM8

Title: Amplified cold transduction in native nociceptors by M-channel inhibition.

Authors: Irina Vetter, Alexander Hein, Simon Sattler, Sabine Hessler, Filip Touska, Elisangela Bressan, Andrés Parra, Ulrich Hager, Andreas Leffler, Stepana Boukalova, Matthias Nissen, Richard J Lewis, Carlos Belmonte, Christian Alzheimer, Tobias Huth, Viktorie Vlachova, Peter W Reeh, Katharina Zimmermann

Journal, date & volume: J. Neurosci., 2013 Oct 16 , 33, 16627-41

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/24133266

Abstract
Topically applied camphor elicits a sensation of cool, but nothing is known about how it affects cold temperature sensing. We found that camphor sensitizes a subpopulation of menthol-sensitive native cutaneous nociceptors in the mouse to cold, but desensitizes and partially blocks heterologously expressed TRPM8 (transient receptor potential cation channel subfamily M member 8). In contrast, camphor reduces potassium outward currents in cultured sensory neurons and, in cold nociceptors, the cold-sensitizing effects of camphor and menthol are additive. Using a membrane potential dye-based screening assay and heterologously expressed potassium channels, we found that the effects of camphor are mediated by inhibition of Kv7.2/3 channels subtypes that generate the M-current in neurons. In line with this finding, the specific M-current blocker XE991 reproduced the cold-sensitizing effect of camphor in nociceptors. However, the M-channel blocking effects of XE991 and camphor are not sufficient to initiate cold transduction but require a cold-activated inward current generated by TRPM8. The cold-sensitizing effects of XE991 and camphor are largest in high-threshold cold nociceptors. Low-threshold corneal cold thermoreceptors that express high levels of TRPM8 and lack potassium channels are not affected by camphor. We also found that menthol--like camphor--potently inhibits Kv7.2/3 channels. The apparent functional synergism arising from TRPM8 activation and M-current block can improve the effectiveness of topical coolants and cooling lotions, and may also enhance TRPM8-mediated analgesia.