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. Author manuscript; available in PMC: 2010 Oct 16.
Published in final edited form as: Cell. 2009 Oct 16;139(2):267–284. doi: 10.1016/j.cell.2009.09.028

Figure 3. Nociceptor diversity.

Figure 3

There are a variety of nociceptor subtypes that express unique repertoires of transduction molecules and detect one or more stimulus modalities. For example, heat-sensitive afferents express TRPV1 and possibly other, as yet unidentified heat sensors; the majority of cold-sensitive afferents express TRPM8, whereas a small subset express an unidentified cold sensor; mechanosensitive afferents express one or more as yet unidentified mechanotransduction channels. These fibers also express a host of sodium channels (such as NaV 1.8 and 1.9) and potassium channels (such as TRAAK and TREK-1) that modulate nociceptor excitability and/or contribute to action potential propagation. Some of these channels are widely expressed among nociceptors, but we illustrate those for which a modality-specific regulatory role has been reported. Three major C-fiber nociceptor subsets are shown here, but the extent of functional and molecular diversity is undoubtedly more complex. Furthermore, the contribution of each subtype to behavior is a matter of ongoing study.