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 estrogen treatment group with 15 rats in each group. Medication was given 2 weeks after ovariectomized. Estrogen treatment 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 drug treatment. The difference of memory function of rats in three groups was observed by conditioned fear training experiment, and the expression of Nogo-A in hippocampus and striatum was observed by immunohistochemistry and Western blotting.     Results  Compared with the sham and estrogen treatment 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). There was no difference between the estrogen treatment group and the sham operation group with the memory function and the Nogo-A expression (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 climacteric women.