Changes in mitocbondHal membrane potential of rat ncllrons following acute brain contusion and laceration injury / 中华神经医学杂志

ABSTRACT

Objective To investigate the changes in mitoehondrial membrane potential of the rat neurons after acute brain contusion and laceration injuries. Methods Seventy Sprague-Dawley (SD)rats were randomized into the sham injury group(n=10)and brain injury group.The brain injury group was divided into 6 subgroups(n=10)for observation at 1,6,and 24 h and 2,3,and 7 days after acutebrain contusion and laceration injury,which was induced by impact of the brain with a flee-falling object.In the brain slices labeled with fluorescent JC-l staining,the changes in the mitoehondrial membrane potential of the neurons were observed under confocal laser scanning microscopy at the indicated time points.The neuronal apoptosis Was detected using Hoehesd3342 staining and TUNEL assay,and the number of apoptotic neurons was determined under optical microscope.The ultrastructural alterations of the neurons were observed with transmission electron microscopy. Results Compared with that of the sham injury group,the mitoehondrial membrane potential of the neurons decreased significantly 1 h alterthe brain injury(P<0.01),reachingthe lowestlevel at 24 h,and maintained the low level aRerwards.Apoptotie neurons were identified in the brain slices with Hochest33342 staining.One hour after the brain injury,TUNEL assay revealed a small number of positive neurons,which increased significantly at 6 h(P<0.01)and reached the highest level at 48 h.The alteration pattern of the number of the positive neurons showed a 24-h delay in compariSOIl witll that of the mitochondrial membrane potential aRer the brain trauma.Under electronmicroscope.the mitocbondria of the neurons exhibited only slight swelling at l h. and obvious morphological changes of the mitochondria occurred 6 h after the brain trauma,accompanied by chromatin fragmentation,presence of marginal nuclei and broadened nuclear membrane;nuclear condensation and chromatolysis were observed in the neurons 24 h after the brain trauma.Conclusion In rats with acute brain contusion and laceration injuries,the mitochondrial membrane potential of the neurons decreases early(<1h)after the brain injury,which induces apoptosis of the neurons.