Inhibitory effects of mild hypothermia on posttraumatic neuronal apoptosis in rats

Objective:To study the mechanisms of posttraumatic neuronal apoptosis and the protective effect of mild hypothermia on posttraumatic brain in the rats.Methods:By using the terminal deoxynucle- tidyl transferase mediated deoxyuridine 5'-triphosphate-bioin nick end labeling technique(TUNEL),agar- ose gel electrophoresis and flow cytometric analysis,the dynamic change in the processes of neuronal ap- optosis in the different brain regions of the rats subjected to severe traumatic brain injury(TBI)were se- quentially examined.The animals were randomly divided into three groups:①sham;②rats with head inju- ry,kiUed at 12,24,48,72,168,336 hours after TBI;③rats with head injury,treated by mild hypothermia at 32℃ for 6,12 and 24 hours respectively.Results:The apoptotic cells could be detectable in the cere- bral cortex,subcortex,white matter and the hippocampus 12 h～14 d after TBI and reached the peak at approximately 12～72h.The apoptotic cells in the above-mentioned brain areas significantly increased in the rats with brain injury compared with the control group(P0.05).Agarose gel electrophoresis showed specific apoptotie zone,and a typical DNA ladder could be revealed by the flow cytometric analysis in the rats with brain injury.In the rats with brain injury treated by mild hypothermia,the apoptotic cells were significantly fewer than those in the rats with brain injury who were not treated by the mild hypothermia (P0.05).Conclusion:The data suggest that apoptosis would occur after TBI.The mild hypothermia may exert favorable effect on inhibition of apoptotic cell death.