Abstract: Objective To study the pathologic diagnosis and the injury time estimation in light closed encephalon injury. Methods Mice were hurt by fluid percussion, and were killed at 15, 30 min, 1, 3 , 6, 12 h, 1, 4, 7,14 d respectively after injury. The expression of Fas-L in the cerebral cortex, thalamus, and hippocampi was detected by immunohistochemistry and the results were assessed by image analysis system. Results It is showed that the expression of Fas-L could be detected in 1 h after injury, and increased significantly in three hours, and it reached apex 12 h after injury, and decreased gradually four days after injury, and returned normal 14 days after injury. Conclusion This research demonstrated that Fas-L mediated apoptosis appeared not only around brain trauma but also in the brain tissue far away from the traumatic area. It indicted that the expression of Fas-L is a useful target for diagnosis of early brain injury; the regularity of Fas-L expression could be used as one of indication to date the time of brain injury.

Key words: fluid percussion brain injury, immunohistochemistry, Fas-L