Fig. 3. Expression of the PSD-95-GFP transgene in the hippocampus and in cultured hippocampal neurons. A, B,Laser confocal microscopy of the CA1 region from the β-actin promoter PSD-95-GFP transgenic mice revealed GFP fluorescence (A, green) in both the stratum radiatum (Rad) and the stratum oriens (Ori). The distribution of PSD-95-GFP was similar to that of synaptophysin immunoreactivity (B, red). C–E, Higher-magnification view of the stratum radiatum of the β-actin promoter PSD-95-GFP transgenic mice. GFP clusters (C, arrows) were in close apposition to the clusters of synaptophysin (D, arrows).E, Superposition of C andD. Pyr, Pyramidal cell layer. Scale bars:A, B, 100 μm; C–E, 5 μm.F, Confocal images of PSD-95-GFP (green) and PSD-95 immunoreactivity (red) in a mixed culture of PSD-95-GFP-expressing neurons and wild-type neurons. Anti-PSD-95 staining in the PSD-95-GFP-expressing neurons (arrows) is slightly higher than that in the wild-type neurons (arrowheads). G, Confocal images of PSD-95-GFP (green) and PSD-Zip45 immunoreactivity (red) in neurons derived from the PSD-95-GFP transgenic mice (arrows) and the wild-type mice (arrowheads). A similar level of anti-PSD-Zip45 staining was observed in two types of cells. Scale bar (F, G), 10 μm. H, Average fluorescence intensity of PSD-95-GFP clusters immunostained with anti-PSD-95 and anti-PSD-Zip45 antibodies. The analysis revealed only 18% overexpression of PSD-95 in the transgenic mice-derived neurons. The difference of the amount of PSD-Zip45 was not statistically significant. C, Neurons derived from wild-type mice;T, neurons derived from PSD-95-GFP transgenic mice.