A-E Hippocampal neuronal apoptosis in both in vitro and in vivo hippocampal neurons after irradiation. DAPI fluorescent images showing pyknosis of in vitro hippocampal neurons exposed to sham-irradiation (A), 30 Gy (B), 30 Gy with roscovitine (in vitro) (C), and 30 Gy with roscovitine (in vivo) (D). Percentage of in vitro and in vivo pyknosis with and without administration of roscovitine (E). *p<0.05 vs. control, #p<0.05 vs. 30 Gy, **p<0.05 vs. 30 Gy+S. S=Saline, R=Roscovitine.