Objective:To investigate the expression of BDNF after traumatic brain injury and postmortem stability Methods:105 healthy SD rats were randomly divided into 4 groups:normal group

sham operation group

traumatic brain injury group and postmortem stability group.The model of brain injury were established by weight-drop impact(traumatic brain injury group and postmortem stability group).After that

the regulation of BDNF expression in each group was detected by immunohistochemistry technique

and evaluated with image analysis technique and statistic system.Results:0.5 hour after impact

the BDNF positive neurons increased in each traumatic brain injury group compared with normal group and sham group.6 hour after injury

The BDNF positive neurons reached the peak number.Then

the BDNF positive cells reduced to normal after 24 hours.but there was no significant difference in BDNF expression among each subgroups of postmortem stability group(P>0.05).Conclusion:There is dependability between the BDNF expression after traumatic brain injury and brain injury time

and postmortem stability is nice at-20℃.