THE GLUTAMATE TRANSPORTER, GLT-1, IS EXPRESSED IN CULTURED HIPPOCAMPAL-NEURONS

There are multiple subtypes of Na+-dependent glutamate transporters. S everal studies suggest that EAAC1 and EAAT4 are expressed in neurons: while GLT-1 and GLAST expression is thought to be restricted to glia. In the present study, expression of GLT-1 and EAAC1 was examined in cu ltured rat hippocampal neurons using single cell mRNA amplification an d immunocytochemistry with subtype specific antibodies. GLT-1 and EAAC 1 mRNAs were observed in all neurons examined. Neuronal phenotype was confirmed in these cells by expression of neurofilament (NF-L) mRNA an d absence of glial fibrillary acidic protein (GFAP) mRNA. EAAC1 immuno reactivity was observed in essentially all cells which expressed neuro n specific enolase (NSE) and GLT-1 immunoreactivity was detected in th e majority (approximately 90%) of NSE-positive cells. Consistent with the glial expression of GLT-1, GLT-1 immunoreactivity was also observe d in NSE-negative cells. These studies provide evidence that GLT-1 exp ression is not intrinsically restricted to glial cells, but can occur in neurons under certain circumstances. (C) 1998 Elsevier Science Ltd. All rights reserved.