BACKGROUND: To evaluate and summarize the effects of cerebral perfusion and vascular reserve on the treatment of SICAS. Recently, research on β-amyloid protein has focused on the regulatory effects of es-trogen or phytoestrogen on its deposition. However, there have been only a few reports on dynamic changes of β-amyloid protein deposition in hippocampus of ovariectomized rats.OBJECTIVE: To measureβ-amyloid protein deposition in the hippocampal formation of ovariectomized rats by using immunohistochemistry; to observe time-dependent dynamic changes. DESIGN: Randomized controlled animal study.SETTING: Third Xiangya Hospital of Central South University.MATERIALS: The experiment was carried out in the Central Laboratory of the Third Xiangya Hospital of Central South University from November 2005 to December 2006. Fifty healthy female Sprague Dawley (SD) rats, weighing (293 ± 10) g, were provided by the Animal Laboratory of Xiangya Medical College, Central South University. All rats had neither a childbearing history nor hepatic or renal disease, or skeletal deformity. Β-amyloid protein immunohistochemical kit was provided by Wuhan Boster Company. The ex-periment was in accordance with animal ethics standards.METHODS: All rats were randomly divided into five groups, including normal control group (n = 10), sham operation group (n = 10), and ovariectomized group (n = 30). After anesthesia in the ovariectomized group, the bilateral ovaries were separated and resected. The same volume of fat was resected in the sham operation group. Rats from the normal control group, however, did not receive any surgical treatments. Rats in the normal control group and sham operation group were sacrificed by anesthesia 7 weeks after surgery. Every ten rats from the ovariectomized group was respectively sacrificed at 7, 15, and 30 weeks after surgery. Immunohistochemistry was used to detectβ-amyloid protein deposition in hippocampal sections. Cell counting and gray value measurements served to record the dynamic changes in β-amyloid protein deposi-tion. MAIN OUTCOME MEASURES: ① Morphological changes. ② Positive cell counts from β-amyloid protein stainings and gray value measurements.RESULTS: All 50 rats were involved in the final analysis. ① Morphological changes. Β-amyloid-positive cells were detected in the hippocampus of all rats. Biebrich scarlet stained neurites with a swollen cytoplasm. A few β-amyloid-positive cells were observed in all groups 7 weeks after surgery, and plasma and neurites were slightly stained. By 15 weeks after surgery, a number of β-amyloid-positive cells were observed in the ovariectomized group, and plasma and neurites were also slightly stained. By 30 weeks after surgery, how-ever, many β-amyloid-positive cells were observed in the ovariectomized group. These cells were partially aggregated and darkly stained. ② Positive cell counts and gray value of β-amyloid protein in hippocam-pus. At 7 weeks after surgery, cell counts and gray value measurements were not significantly different in the ovariectomized group compared to the sham operation group and normal control group (P > 0.05). Cell counts and gray value measurements were higher in the ovariectomized group by 15 weeks compared to tho-se by 7 weeks in the normal control group, sham operation group and ovariectomized group (P < 0.05). At 30 weeks after surgery, cell counts and gray value measurements were higher in the ovariectomized group compared to the normal control group. In addition, there were significant differences between sham opera-tion group and ovariectomized group at 7 and 15 weeks after operation (P < 0.05–0.01). Cell counts and gray value measurements increased in all groups over time.CONCLUSION: Extended estrogen deficiency in rats can increase β-amyloid protein deposition in the hippocampus and the deposition increases over time.