Fig. 3.

Expression and regulation by growth factors of kainate receptor subunit RNAs in purified cortical O-2A progenitor cells. Northern blot analysis was performed by using total RNA;lanes show, from left toright: Type-1 astrocyte RNA (ASTROS; 15 μg/lane) isolated from one set of cultures; RNA (15 μg/lane) pooled from four separate sets of O-2A cultures, each set tested with all of the treatments analyzed; cerebral cortex RNA (P1 cortex; 15 μg/lane) isolated from postnatal day 1 rat cerebral cortex. O-2A cells and type-1 astrocytes were cultured for 3 and 10 d, respectively. N1, N1 medium + 0.5% FBS;PDGF, same medium supplemented with 10 ng/ml of PDGF;bFGF, same medium supplemented with 10 ng/ml of bFGF;PDGF+bFGF, same medium supplemented with 10 ng/ml of PDGF and bFGF each. Numbers on the leftrepresent molecular size in kilobases, as derived from an RNA standard. Blots were rehybridized with a cDNA probe for 18S rRNA to control for uniform RNA loading; the bottom panel shows the result obtained with rehybridization of the KA1 blot. All blots were exposed to film for 4 d to maximize signal detection. No expression of GluR5 was detected by Northern blot in cultured glia under any culture condition, even after longer exposure times (see also Patneau et al., 1994). Histograms in the right panels were derived for PhosphorImager analysis of the corresponding blots. The experiments was repeated by using an independent set of cultures with similar results. All data are presented as ratios over untreated cells (N1).