Abstract: Abstract Objective： To observe the effect of progesterone on the expression of gial fibrillary acidic protein in brain tissue with hypoxia-ischemia brain damage in neonatal rats, and discuss the protective mechanism of progesterone hypoxic-ischemic encephalopathy of neonatal rats. Methods ： Twenty four 7-day-old neonatal rats were randomly divided into three groups: sham-operated group, hypoxia-ischemia group and pretreatment group. Rats in hypoxic-ischemic group and pretreatment groups were subjected to left common carotid artery ligation, then were exposed to 80mL/L oxygen and 920mL/L nitrogen gas in 37℃ closed container for up to 2.5h to establish HIE model. Progesterone was injected intraperitoneally into the pretreatment groups rats respectively at 30 minutes before hypoxia, Solution was injected into the first two groups. All rats were killed at the 24 hour after operations, immunohistochemistry staining and RT-PCR were used to examine the expression of GFAP in brain. Results： GFAP was expressed in every group rat. The number of GFAP positive staining cells and the expression of GFAP in hypoxic-ischemic group were significantly higher than that in the sham-operated group. The number of GFAP positive staining cells and the expression of GFAP in pretreatment group were significantly lower than that in the hypoxic-ischemic group（P<0.01）. Conclusion： The hypoxic-ischemic brain damage may induce significant increase of GFAPexpression in brain tissue of neonatal rat. Progesterone can inhibit the raising of astroeyte induced by hypoxia-ischemia brain damage, so it plays protective role by Anti- hypoxic-ischemic brain damage.

Key words: progesterone, astrocytes, gial fibrillary acidic protein, hypoxia-ischemia brain damage, neonatal rats