Expression of tetrodotoxin-resistant sodium channels in capsaicin-sensitive dorsal root ganglion neurons of adult rats.

We have used conventional whole-cell electrophysiological recording techniques to measure the level of expression of tetrodotoxin-sensitive (TTX-S) and tetrodotoxin-resistant (TTX-R) sodium currents in the capsaicin-sensitive and capsaicin-insensitive subpopulations of dorsal root ganglion neurons. We find that there are significantly higher levels of TTX-R expressed in the capsaicin-sensitive group but no difference in the levels of TTX-S. Since capsaicin is a selective stimulant of polymodal nociceptors, these data raise the possibility that TTX-R sodium channels may be an important determinant of nociceptor phenotype.