Abstract: Objective：Investigate the effects of exogenous estrogen on the expression of nuclear transcription factor（Nrf2），heme oxygenase-1（HO-1），silent information regulator 1（SIRT1），and the changes of the neuronal morphology and volume in the hippocampus and cortex of those ovariectomized rats，so as to explore the beneficial effects of estrogen on the nervous system. Methods：Forty female Sprague-Dawley（SD） rats aged three months were randomly divided as follows：①control group（CON），②sham operation group（SHAM），③ovariectomized group（OVX），④treated group（OVX+E2）. There were 10 rats in each group. The OVX+E2 group were treated with 17β-oestradiol intragastric administration，the other groups were given saline daily. After 16 weeks，Nrf2/HO-1 and SIRT1 levels in the hippocampus and cortex were detected by immunohistochemistry. Then observe the morphology of neurons from cerebral cortex and hippocampus CA1 region. Results：①Compared with the SHAM group，the Nrf2/HO-1 level in hippocampus and cortex of the OVX group was significantly increased，while SIRT1 level was significantly decreased ；Compared with the OVX group，Nrf2 and SIRT1 level of the OVX+E2 group was significantly increased，while HO-1 level was significantly decreased. ②There were not significant differences in the number and arrangement of neurons between OVX+E2 group and SHAM group，and the number of tigroid body in hippocampus and cortex of the OVX group was reduced，the morphological alteration of the neuron were disordered. Conclusions：Exogenous oestradiol increased the Nrf2/SIRT1 level but reduced HO-1 level in the hippocampus and cortex of the ovariectomized rats，maintaining neuronal number and structure，thereby protecting the nervous system.

Key words: Estrogens, Heme oxygenase (decyclizing), Transcription factors, Silent information regulator 1, Nervous system