抄録
It is reported that thermosensitive TRP channels (thermo TRPs), TRPV1, TRPV2, TRPA1 and TRPM8 are expressed in adult mouse DRG neurons to exert nociception and/or thermosensation. In general, it is well known that ion channels have distinct roles between embryonic and adult stages, suggesting that the thermo TRPs might also have unexpected specific roles in embryonic neurons compared with those in adult ones. Interestingly, little investigation has been performed to identify when the thermo TRPs are expressed in developing DRG and spinal cord. Identifying expression timing of the channels is necessary to clarify their specific roles in embryo. Therefore, we examined the expression profiles of TRPV1, TRPV2, TRPA1 and TRPM8 in developing mouse DRG and spinal cord by in situ hybridization. Surprisingly, the expression of those thermo TRPs in DRG was already observed in early embryonic stages, and some of them were observed in motor neurons in spinal cord as well, suggesting that those channels might have specific roles in the embryonic stages such as the regulation of cell migration and axon extension. Therefore, we examined whether activation or inhibition of the thermo TRP activities can alter cell migration or axon extension in DRG explant culture from embryonic mice. We found the activation states of thermo TRPs influenced the properties of axon extension. Thus, we for the first time revealed that thermo TRPs have two distinct roles, regulation of neural maturation in embryonic stage and nociception and/or thermosensation in adult stage. [J Physiol Sci. 2008;58 Suppl:S51]
