Rapid Communication The glutamate transporter, GLT-1, is expressed in cultured hippocampal neurons

There are multiple subtypes of Na+-dependent glutamate transporters. Several 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 cultured rat hippocampal neurons using single cell mRNA amplification and immunocytochemistry with subtype specific antibodies. GLT-1 and EAAC1 mRNAs were observed in all neurons examined. Neuronal phenotype was confirmed in these cells by expression of neurofilament (NF-L) mRNA and absence of glial fibrillary acidic protein (GFAP) mRNA. EAAC1 immunoreactivity was observed in essentially all cells which expressed neuron specific enolase (NSE) and GLT-1 immunoreactivity was detected in the majority (approximately 90%) of NSE-positive cells. Consistent with the glial expression of GLT-1, GLT-1 immunoreactivity was also observed in NSE-negative cells. These studies provide evidence that GLT-1 expression is not intrinsically restricted to glial cells, but can occur in neurons under certain circumstances.