Objective:To investigate aquaporin4(AQP4) expression and blood-brain barrier(BBB) permeability after intracerebral injection of tumor necrosis fctor-alpha(TNF-α) so as to explore the mechanism of brain edema induced by TNF-α in the rats.Methods:Forty-five adult SD rats

which were used to detected brain water contents and AQP4 expression were divided randomly into groups:control group(Group A with 5 rats)

normal sodium group(NS Group with 20 rats)

tumor necrosis fctor-alpha group(TNF-α Group with 20 rats).The NS groups and the TNF-α groups were studied after the microinjection at an interval of1h

6h

24h and 72h

respectively(n=5 for each group).Other Forty-five adult SD rats were used detected BBB permeability.The grouping approach was the same as the former.The brain edema models were established by microinjection of TNF-α into the cortex.We detected brain water contents by dry-wet weight method

AQP4 mRNA expression by RT-PCR and BBB permeability by EB method.Results:Brain water contents reached peak at 6 hours and gradually recovered normal level at 72h after intracerebral injection of TNF-α.AQP4 mRNA expression wasn’t obvious at 1h(P>0.05)

peaked at 6h and it was higher than normal at 72h(P<0.05).The level of EB contents rose at 1h

peaked at 6h

then descended gradually.There was a significantly positive correlation between AQP4 mRNA expression and BBB permeability(R=0.839

P<0.01).Conclusions:TNF-α may have a function in the development and deterioration of the brain edema via up-regulating AQP4 expression and increasing BBB permeability.