Abstract: Objective To investigate the expression changes in aquaporin-4(AQP4) during brain traumatic edema in rat,and evaluate its relationship with the disruption of blood-brain barrier(BBB) permeability.Methods Ninety-four SDrats were randomly allocated into control group,sham operation group and brain injury group,with the last group further divided into groups of 1,6,24,48 and 168 h after rat brain injury.In a rat impact-acceleration head injury model,brain water contents were measured by wet-dry weight method,BBB permeability was evaluated by immunohistochemical staining of IgG,and the expressions of AQP4 and GFAP in brain were determined by immunohistochemical stain and Western blotting.Results After rat brain trauma,cerebral water content of injured brain increased significantly at 6 h,and reached maximum at 24 h.The extravasation of IgG in injured brain occurred at 1 h,and peaked at 6h.Western blotting study detected enhancement AQP4 expression adjacent to injury site after brain trauma,and immunostaining revealed the changes in AQP4 polar distribution in the reactive astrocyte,with increased AQP4 expressions both in the peri-vascular astrocyte end-feet and cell body.The time course of enhanced AQP4 expressions was accompanied with the increase of brain water content and delayed after the maximum extravasation of IgG.Conclusion Enhanced expressions of AQP4 followed the disruption of BBBpermeability,which means it may contribute to the development of brain edema after rat traumatic brain injury.

Key words: traumatic brain injury, brain edema, aquaporin-4, blood-brain barrier