The Study Between The Expression Of Aquaporin-4and Brain Edema In Hypoxic-ischemic Brain Of Neonatal Rats

Objective: To investigate the change of aquaporin-4expression inthe brain tissues during hypoxia in neonate rat and explore its involvementin brain edema.Methods: Ten-day-old healthy SD rats were randomly divided intocontrol and experimental groups. Experimental groups were divided into2h,4h,8h,16h sub-groups after inducing hypoxic-ischemic (HI) byligating the right common carotid artery; the control groups weresham-operated. The behavioral change in each group was monitored andtheir brains recovered2h、4h、8h and16h after treatment, and thehistological changes were examined with hematoxylin-eosin (HE) staining.The expression of AQP4protein was detected with immunohistochemistry(IHC). The change of AQP4mRNA expression was examined withfluorescence quantitative PCR (FQ-PCR).Result: The neuroethology and histological structure were notsignificantly changed in the control group, while the experimental groupshowed different levels of nervous symptoms. HE staining showed that thebrain tissue especially in CA1area of hippocampus had hypoxia-ischemiachange. For example, the space around the cells became larger, some of theneurons showed necrosis, the plasmalemma were cleaved, and the nucleiwere either deeply stained or disappeared. The IHC analysis showed theexpression of AQP4in the hippocampus, choroid plexes, brain cortex,thalamus and other regions. The expression of AQP4protein was down-regulated with the hypoxic-ischemic (HI) time. The IHC analysisshowed that the optical density value of CA1area of hippocampus in thecontrol group and hypoxic (HI2h, HI4h, HI8h, HI16h) groups is0.304±0.023,0.259±0.031,0.209±0.040,0.141±0.030,0.109±0.013respectively (P＜0.05).The results of FQ-PCR showed that the expressionof AQP4mRNA of the brain tissue in the hypoxic (2h,4h,8h,16h) groupsis0.835、0.768、0.650、0.493folds of the its expression levels in the controlgroup respectively.Conclusion: The brain edema was aggravated, neurons irreversiblydamaged, and the expression of AQP4down-regulated after the inductionof hypoxic-ischemic (HI) condition, suggesting that AQP4could participatein the development of cerebral edema and brain damage in the neonatal ratunder the hypoxic-ischemic (HI) condition.