EXPRESSION OF THE MESSENGER-RNA FOR THE BETA-2 SUBUNIT OF THE VOLTAGE-DEPENDENT SODIUM-CHANNEL IN RAT CNS

Expression of the voltage-dependent sodium channel has been analysed i n adult rat central nervous system by Northern blotting and in situ hy bridization. Northern blots showed that all the territories studied ex press beta 2 transcripts, albeit with widely varying levels (with cere bellum much greater than hippocampus > brain > brainstem > spinal cord ). In situ hybridization confirmed that in these structures, all the n euronal cell bodies contain beta 2 mRNA; expression was particularly h igh in the granule cells of the cerebellum, in both pyramidal cell lay er and dentate gyrus in the hippocampus, and in spinal cord motor neur ons. Northern blots also showed that RNA extracted from optic nerve an d cultured cortical astrocytes contained beta 2 mRNA, while it was tot ally absent from sciatic nerve. In situ hybridization evidenced the pr esence of a numerous population of beta 2-positive cells in cerebellum white matter, spinal cord white matter, and in corpus callosum, where frontal sections showed labelled cells arranged in the chain-like or row pattern typical of interfascicular oligodendrocytes. Combination o f antiglial fibrillary acid protein (GFAP) immunofluorescent histochem istry with detection of beta 2 mRNA evidenced that expression of the t ranscripts was indeed restricted to GFAP-negative cells in white matte r.