Expression of mRNA for a sodium channel in subfamily 2 in spinal sensory neurons.

RNA blot analysis and non-isotopic in situ hybridization cytochemistry were used to study the expression of the mRNA for the glial sodium channel NaG, belonging to Na+ channel subfamily 2, in rat dorsal root ganglia (DRG). mRNA hybridizing at high stringency with an antisense riboprobe against the NaG sequence was observed in both Schwann cells and spinal sensory neurons in situ within DRG, but was expressed at higher levels in the latter. In contrast, hybridization was not detectable in neurons within hippocampus, cerebellum and spinal cord. The expression of the mRNA hybridizing with the NaG probe appears to be developmentally regulated in both Schwann cells and DRG neurons, with levels increasing as development proceeds. Thus, in addition to the mRNAs for types I and II/IIA alpha-subunits and beta 1-subunit in DRG neurons and types II/IIA and III alpha-subunits beta 1-subunit in Schwann cells, the mRNA for an additional sodium channel belonging to subfamily 2 is expressed in these cells in situ.