DIFFERENTIAL NA-1 SUBUNIT MESSENGER-RNA EXPRESSION IN STELLATE AND FLAT ASTROCYTES CULTURED FROM RAT CORTEX AND CEREBELLUM - A COMBINED IN-SITU HYBRIDIZATION AND IMMUNOCYTOCHEMISTRY STUDY( CHANNEL BETA)

Astrocytes have been shown to express voltage-sensitive Na+ channels, but the molecular structure of these channels is not yet known. Recent studies have demonstrated the expression of rat brain voltage-sensiti ve Na+ channel mRNAs in astrocytes. In this study, we used a combined non-radioactive in situ hybridization/ immunocytochemistry method to i nvestigate the expression of voltage-sensitive Na+ channel beta 1 subu nit (Na beta 1) mRNA in definitively identified, GFAP-positive astrocy tes cultured from two different regions of the rat brain, cerebrum and cerebellum. In general, two morphologically distinct types of GFAP-po sitive astrocytes were observed in culture: flat, fibroblast-like and stellate, process-bearing. We observed a differential expression of Na beta 1 mRNA in GFAP-positive astrocytes: 1) stellate astrocytes expre ssed Na beta 1 mRNA, although the level of Na beta 1 mRNA expression w as variable, and 2) flat astrocytes generally did not express Na beta 1 mRNA. Moreover, Bergmann-like cells from cerebellum did not express Na beta 1 mRNA, while the granule cells associated with Bergmann-like cell expressed Na beta 1 mRNA. These observations indicate that Na bet a 1 mRNA is differentially expressed in rat astrocytes with various mo rphologies in vitro. (C) 1995 Wiley-Liss, Inc.