title: Cutaneous TRPM8-expressing sensory afferents are a small population of neurons with unique firing properties.
abstract: It has been well documented that the transient receptor potential melastatin 8 (TRPM8) receptor is involved in environmental cold detection. The role that this receptor plays in nociception however, has been somewhat controversial since conflicting reports have shown different neurochemical identities and responsiveness of TRPM8 neurons. In order to functionally characterize cutaneous TRMP8 fibers, we used two ex vivo somatosensory recording preparations to functionally characterize TRPM8 neurons that innervate the hairy skin in mice genetically engineered to express GFP from the TRPM8 locus. We found several types of cold-sensitive neurons that innervate the hairy skin of the mouse but the TRPM8-expressing neurons were found to be of two specific populations that responded with rapid firing to cool temperatures. The first group was mechanically insensitive but the other did respond to high threshold mechanical deformation of the skin. None of these fibers were found to contain calcitonin gene-related peptide, transient receptor potential vanilloid type 1 or bind isolectin B4. These results taken together with other reports suggest that TRPM8 containing sensory neurons are environmental cooling detectors that may be nociceptive or non-nociceptive depending on the sensitivity of individual fibers to different combinations of stimulus modalities.
authors.affiliation: Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Jankowski
authors.affiliation: Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania.
authors.forename: Kristofer K
authors.initials: KK
authors.lastname: Rau
authors.affiliation: Department of Neurobiology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania rkoerber@pitt.edu.
authors.forename: H Richard
authors.initials: HR
authors.lastname: Koerber
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D003080:Cold Temperature; D037102:Lectins / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D018408:Patch-Clamp Techniques; D011984:Sensory Receptor Cells / Q000378:metabolism*; D012867:Skin / Q000294:innervation* / Q000378:metabolism; D050053:TRPM Cation Channels / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000378:metabolism
chemical_list: D037102:Lectins; D050053:TRPM Cation Channels; C492297:TRPM8 protein, mouse; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D015740:Calcitonin Gene-Related Peptide
keywords: Cold sensation; nociception; sensory neurons; somatosensation