Effect Of Dexamethasone On Aquaporin-4 Expression After Intracerebral Hemorrhage In Rats

Objective: To study efectt of dexamthasone on aquaporin-4 expression in rats after intracerebral hemorrhage and the significance.Methods: one hunderd thirty SD rats were randomly divided into three groups: slam-operation group (n=10), control group (ICH) (n=60), DEX group (n=60). The last two groups was further divided into the groups of 6h, 12h, 24h, 3d, 5d, 7d (n=10 in each group). The control group: rats received an intracerebral injection of 0.4u collagenase followed by saline (1mg/kg i.p). The DEX group: rats received an intracerebral injection of 0.4u collagenase followed by DEX (1mg/kg i.p) injection every 24h. The immunohistochemical (IHC) expression of AQP4 after intracerebral hemo- rrhage were determined by using immunohistochemistry. The brain water content were measured by using the dry-wet weight assay.Results: With prolonged bleeding time, water content in rat brain after intracerebral hemorrhage increased to 3 day after intracerebral hemorrhage, reached the climax. Afterwards, rat brain tissue water content decreased gradually, and sustainable for more than seven days, one of 1,3,5-day time point was significantly higher than sham-operated group (P<0.05). In DEX group, with prolonged bleeding time, rat brain tissue water content increased to 3 day after intracerebral hemorrhage, reached the peak, but one of 1, 3, 5-day time point was significantly lower than control group (P<0.05). Compared with the sham-operated group, aquaporin-4 (AQP4) immunohistochemical reaction of edema area around the hematoma region enhanced with the prolongation of bleeding time (the level of AQP4 expression enhancement), and peaked at the post-ICH 3 day (P<0.05). Compared with the control group, in DEX group, the level of AQP4 expression decreased, especially at the 3 day (P<0.05).Conclusion: our results showed that AQP4 was expressed in brain areas around hemorrhage core, which was invovled in brain fluid formation and accumulation. Dexamethasone treatment can reduce the brain water content of intraerebral hemorrhage model in rats. Dexamethasone treatment can reduce aquaporin4 expression in dose-dependent manner and dexamethasone in low dose used in ealy stage may reduce brain edema.