Abstract: Objective: To construct the brain tissue damage models of newborn rats induced by hyperoxia,and to explore the effect of hyperoxia on the natriuretic peptide receptor-cyclic guanosine monophosphate(NRP-cGMP) signaling pathway in brain tissue of the newborn rats. Methods: A total of 60 newly born Wistar rats were divided into control group and hyperoxia model group,and there were 30 rats in each group. At the 1st,3rd and 7th days after hyperoxia exposure,the brain tissues of 10 rats randomly selected from each group were gotten,and the body weights of the rats in two groups were detected.HE staining was used to observe the morphology of brain tissue of the rats in two groups;the ultrastructures of brain tissue of the rats in two groups were observed under transmission electron microscope.Western blotting method was used to detect the expression levels of natriuretic peptide receptor A (NPR-A) and natriuretic peptide receptor B (NPR-B) in brain tissue of the rats in two groups.ELISA method was used to determine the levels of cGMP in brain tissue of the rats in two groups. Results: The body weight of the rats in hyperoxia model group was significantly lower than that in control group at the 1st,3rd and 7th days after hyperoxia exposure(P<0.05).The HE staining results showed that at the 3rd day after hyperoxia exposure,the volume of the hippocampal pyramidal cells of the rats in hyperoxia model group was reduced, and the arrangement was sparse;at the 7th day after hyperoxia exposure,the hippocampal cells showed deep staining and shrinkage, and the cell boundaries were not clear. Under electron microscope,at the 3rd day after hyperoxia exposure, the mitochondrial double membrane structure of the rats in hyperoxia model group was destroyed,a few crest disappeared,and the number of mitochondria and synapses was decreased; the above damage conditions were aggravated at the 7th day after birth.The Western blotting results showed that at the 1st,3rd and 7th days after hyperoxia exposure,the expression level of NPR-A in brain tissue of the rats in hyperoxia model group was higher than that in control group(P<0.05).But only at the 1st day after hyperoxia exposure,the expression level of NPR-B in brain tissue of the rats in hyperoxia model group was higher than that in control group(P<0.05).The ELASA results showed that at the 1st,3rd and 7th days after hyperoxia exposure, the level of cGMP in brain tissue of the rats in hyperoxia model group was higher than that in control group(P<0.05). Conclusion: NRP-cGMP signaling pathway is involved in the occurrence of brain injury induced by hyperoxia.

Key words: hyperoxia, brain injury, cyclic guanosine monophosphate, natriuretic peptide receptor, rat,Wistar