THE BETA-1 SUBUNIT MESSENGER-RNA OF THE RAT-BRAIN NA-CELLS( CHANNEL IS EXPRESSED IN GLIAL)

Although the molecular characteristics of glial Na+ channels are not w ell understood, recent studies have shown the presence of mRNA for rat brain Na+ channel alpha subunits in astrocytes and Schwann cells. In this study, we asked whether the mRNA for the rat brain Na+ channel be ta 1 submit is expressed in glial cells. We performed in situ hybridiz ation using a complementary RNA probe for the coding regions of the ra t brain Na+ channel beta 1 subunit mRNA and detected beta 1 subunit mR NA in cultured rat optic nerve astrocytes and sciatic nerve Schwann ce lls. The beta 1 subunit was amplified by reverse transcription-polymer ase chain reaction in rat optic and sciatic nerves, which lack neurona l somata but contain astrocytes and Schwann cells, respectively. Doubl et bands of the beta 1 subunit mRNA were amplified from both optic and sciatic nerves. Through the cloning and sequencing of these bands, we confirmed the amplification of a mRNA highly homologous to the previo usly cloned rat brain Na+ channel beta 1 subunit (beta(1.1)) and a nov el form of the beta 1 subunit mRNA (beta(1.2)), which is closely homol ogous to P-1.1 but contains an additional 86-nucleotide insert in 3' n oncoding regions. Two beta 1 subunit mRNAs were also amplified from ra t brain and skeletal muscle, but not from rat liver or kidney. These r esults indicate that rat brain Na+ channel beta 1 subunit mRNAs are ex pressed in glial cells as well as in neurons.