Our research objectivis to study the effect of NaoHuanDan on the ultrastructure of the hippocampal CA3 and brain cortical neurons in the ovariectomized rat by means of transmission electron microscopy.Forty female Sprague-Dawley rats were randomly divided into four groups: Control group

conjugated estrogen group

and NaoHuanDan groups

and experimental drugs or placebo were orally administrated per day for 6 months from day 7 of having been ovariectomized. The ultrastructure of hippocampal CA3 and brain cortical neurons' changes were observed under transmission electron microscope after routine perfusion

fixation

drawing materials

slicing up and staining. Results showed that there were obvious degeneration and necrosis in the mitochondrias and other organelles in the control group

accumulation of lipofucin in the cytoplasm. And degeneration of synapses and blurred of the synapse connection

but all these symptoms were significantly reduced after having been treated with conjugated estrogen and NaoHuanDan.