We analyzed the expression and regulation of glutamate receptor subunits in the rat neural tube (10 day embryos) and in cell cultures derived from this tissue. In the cultures, all cells were stained with antibodies against the neural progenitor marker nestin. More than 50% of the cells were also stained by the monoclonal antibodies LB1 or A2B5, which bind to neuronal and glial progenitors. Approximately 6% of the cells were stained with antibodies for the low affinity NGF receptor, a neural crest cell marker. A small percentage of cells differentiated to neurons or astrocytes, as determined by staining with anti-neurofilament and anti-GFAP antibodies, respectively. RT-PCR analysis of neural tube tissue and culture mRNAs demonstrated that the AMPA receptor subunits GluR3 and 4 and the kainate receptor subunits GluR6, 7, KA1 and KA2 were detectable at E10. The kainate receptor subunits GluR6 and KA2 were upregulated by culture conditions which stimulated cell differentiation, as determined by concomitant downregulation of nestin mRNA. Both in neural tube tissue and in cultured cells, GluR6 was 100% unedited. Finally, both GluR6 and KA2 proteins could be detected in subpopulations of neural progenitors and differentiated neurons. Our data indicate that kainate receptor genes are expressed in undifferentiated progenitor cells of the neural tube at E10, and are upregulated during neural cell differentiation.