[Abstract] Objective To elucidate the important role of Nogo-A in climacteric neurodegeneration such as memory impairment by observing memory function and the expression of Nogo-A in hippocampus and striatum of rats under low estrogen condition. Methods Fouthy-five female SD rats were divided into sham operation group, ovariectomized group and ovariectomized estrogentreatment group with 15 rats in each group. Medication was given 2 weeks after ovariectomized. Estrogentreatment group was subcutaneously injected in groin with estrogen [25 μg/ (kg.d)] dissolved in sterile sesame oil. The sham operation group and the ovariectomized group were given the same amount of aseptic sesame oil. Samples were collected after 6 weeks of drugtreatment. The difference of memory function of rats in three groups was observed by conditioned feartraining experiment, and the expression of Nogo-A in hippocampus and striatum was observed by immunohistochemistry and Western blotting. Results Compared with the sham and estrogentreatment group, memory function in ovariectomized group decreased significantly and the number of Nogo-A positive neurons in hippocampus and striatum of ovariectomized rats was significantly higher than that of sham operation group (P 0. 05). The result of immunoblotting was consistent with the above-mentioned immunohistochemical result. Conclusion The increased expression of Nogo-A in hippocampus and striatum under low estrogen condition may be one of the key reasons for memory impairment in climactericwomen.