Abstract: Objective: To characterize 5-month-old ovariectomized and 18-month-old female rats as models for menopausal females. Methods: Sexual hormones FSH, LH and E₂ were measured in serum and hypothalamus, and superoxide dismutase（SOD）, malondialdehyde（MDA）and total anti-oxidative capacity（T-AOC）in hypothalamus of a total of 71 Sprague Dawley female rats of 4 groups: 5-month-old control group, 5-month-old ovariectomized model group, 18-months-old model group and 24-month-old aged control group. Mitochondria DNA damage was monitored by measuring expression level of mRNA of CoⅠ and CoⅢ using quantitative RT-PCR. Ultrastructure of mitochondria of hypothalamus neuron cells was investigated using transmission electron microscope. Results: Compared with 5-month-old control rats, FSH and LH increased and E₂ decreased in serum and hypothalamus significantly（P<0.05）in both 5-month-old ovariectomized rats and 18-month-old rats. Antioxidants SOD and T-AOC of hypothalamus were reduced significantly in 5-month-old ova-riectomized rats and 18-month-old rats（P<0.01）. The expression levels of CoⅠ and Co Ⅲ, indications of hypothalamus mitochondria DNA damage, were at lowest in 5-month-old controls rats followed by ovariectomized 5-month-old rats, 18-month-old rats and 24-month-old rats（P<0.001）. Ultrastructural impairment of mitochondria of hypothalamic neuron cells was visible in both 5-month-old ovariecto-mized rats and 18-month-old rats. Conclusion: Both 5-month-old ovariectomied rats and 18-month-old rats have sexual hormones changes similar to that of menopausal females. Removal of bilateral ovaries in young rats not only lead to hormonal change but also results in mitochondria aging as 18-month-old rats have. Thus both 5-month-old ovariectomized rats and 18-month-old rats may mimic the status of sex endocrine change and hypothalamus aging in menopause females.

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