Transient Receptor Potential (TRP) Channels as a Mediator of Tooth Pain

Abstract

Dental primary afferent neurons and odontoblasts are cellular components by which noxious stimuli are perceived as painful by teeth. Our lab tries to elucidate molecular mechanisms underlying these transmission processes. Tooth pain is commonly induced by hot or cold substances. Temperature signaling can be initiated by members of transient receptor potential family (thermo-TRP) channels. We hypothesized that thermo-TRP channels expressed by dental primary afferent neurons and/or odontoblasts mediate tooth pain evoked by noxious thermal stimuli. Single-cell RT-PCR and immunohistochemistry revealed expression of TRPV1, TRPM8 and TRPA1 in subsets of such neurons. Capsaicin (a TRPV1 agonist), menthol (a TRPM8 agonist) and icilin (a TRPM8 and TRPA1 agonist) increased intracellular calcium and evoked cationic currents in subsets of neurons, as did the appropriate temperature changes (>42°C, <25°C and <17°C respectively). Individual neurons sometimes expressed two or three channels, and responded to two or three corresponding stimuli. Subfamilies of thermo-TRP channels were not only expressed but also functionally working in odontoblasts. The results suggest that activation of thermo-TRP channels expressed by dental afferent neurons and/or odontoblasts contributes to tooth pain evoked by temperature stimuli. Accordingly, blockade of thermo-TRP channels will provide a novel therapeutic intervention for the treatment of tooth pain [J Physiol Sci. 2007;57 Suppl:S36]