Figure 3. γH2AX immunostaining counterstained with hematoxylin shows that γH2AX foci are almost undetectable in the stratum pyramidale of CA1 area of the hippocampus (A) of P4 mice without irradiation. Irradiation with 5Gy induced obvious γH2AX foci (arrows) in the stratum pyramidale of CA1 area (B, C is magnified from the ellipse in B) at 1 day after irradiation at P3. Similarly, γH2AX foci are undetectable in the blood vessel of the hippocampus (A’) of P4 mice without irradiation. Irradiation induced obvious γH2AX foci (arrows) in the hippocampal blood vessel (B’, C’ is magnified from the ellipse in B’) at 1 day after irradiation at P3. Scan bar=25μm in (A) applies to (B–C) (A’–C’).