Changes in three subtypes of tetrodotoxin sensitive sodium channel expression in the axotomized dorsal root ganglion in the rat.

The upregulated expression of tetrodotoxin sensitive (TTXs) Na+ channels is thought to play an important role in the development of ectopic discharges (EDs) in axotomized sensory neurons. The present study examined the levels of mRNAs of three subtypes of TTXs Na(+) channels, Na(v)1.7, Na(v)1.6, and Na(x), in the dorsal root ganglion (DRG) after segmental spinal nerve ligation. Following nerve ligation, the level of mRNAs of Na(v)1.7 and Na(v)1.6 was decreased, while the Nax mRNA level was increased at 5 days, but not at 1 day, postoperatively compared with the normal levels. Thus, if upregulated expression of TTXs Na+ channels contributes to the generation of EDs in axotomized DRG neurons, Na(x) is the most likely contributor among the three tested subtypes.