A-F Hippocampal neuronal apoptosis in CA1 region in rats after irradiation. DAPI fluorescent images showing hippocampal neuronal apoptosis in rats with sham-irradiated control (A), irradiation of 10 Gy (B), 20 Gy (C), 30 Gy (D), and 30 Gy+R (E). The cells were counted in a 1 mm length of the middle portion of hipocampal CA1 region under bright-filed microscopy. n=6 for each group. *p<0.05 in 20 Gy and 30 Gy vs. control, *p<0.05 in 30 Gy+R vs. 30 Gy+S. R=Roscovitine, S=Saline.