Combined effect of E2 and progestin on neurogenic activity and apoptosis in vivo. Vehicle, 30 μg/kg BW E2, and 30 μg/kg BW progestins combined with 30 μg/kg BW E2 were injected to 3-month-old OVX female rat followed by BrdU injection 1 h later. A, Effects of E2 and E2 + progestins on PCNA expression level in hippocampus. B, Combined effect of E2 + progestin in regulating BrdU+ cell count in the hippocampus of OVX adult female rat. *, P < 0.05 and **, P < 0.01 compared with vehicle control; †, P < 0.05 compared with E2-alone group. C, Effects of E2 and E2 + progestins on CVα expression at protein level. Western blot analysis was conducted on protein isolated from hippocampus. D, Effects of E2 and E2 + progestins on Bax/Bcl-2 expression at protein level. E, Combined effect of E2 + progestin in regulating TUNEL+ cell count in the hippocampus of OVX adult female rat. *, P < 0.05 and **, P < 0.01 compared with vehicle control; †, P < 0.05 and ††, P < 0.01 compared with E2 group.