脑缺血再灌注后小鼠海马神经元两种不同的形态学改变

Two kinds of morphological changes of hippocampal neurons after ischemia reperfusion in mice

目的:用小鼠脑缺血再灌注的海马标本观察神经元损伤的形态学改变,以期探讨不同亚区神经元损伤的病理生理特点。方法:小鼠33只随机分为模型组24只及对照组9只。用双侧颈总动脉反复夹闭方法制作脑缺血再灌注动物模型,造模后存活模型组18只,对照组9只。于再灌注后24,72h,7d取材,观察海马神经元的超微结构改变。原位DNA末端标记法检测核DNA断裂。结果:再灌注24h锥体细胞内线粒体肿胀,粗面内质网消失,细胞核内异染色质稍浓缩;再灌注72h锥体细胞内异染色质浓缩,变暗,颗粒细胞出现核膜凹陷及局部扩张;再灌注7d锥体细胞表现为核碎裂等,颗粒细胞染色质浓缩呈圆形团块。光镜下可见TUNEL染色阳性的锥体细胞及颗粒细胞。结论:海马不同区对缺血性损伤的易患性不同,CA1区锥体细胞最敏感,显示了以迟发性坏死为主的超微结构改变,颗粒细胞显示了凋亡样改变。

AIM:To observe the morphological changes of hippocampal neurons after ischemia reperfusion in mice so as to probe into the pathophysiological characters of neuron subregion after injury. METHODS: Thirty three mice were randomly divided into experimental group(n=24) and control group(n=9).The ischemia reperfusion animal models were made by repeated clamping bilateral common carotid arteries. After establishment of the models,there were 18 rats surviving in the model group,and 9 in the control group.Samples were collected 24 hours,72 hours and 7 days after reperfusion separately.Ultrastructural change of hippocampal neurons was observed.Nuclear DNA fragmentation was observed with in situ end labeling of DNA method. RESULTS:Twenty four hours after reperfusion, mitochondrias in the cells were swollen;rough endoplasmic reticulum disappeared from the cytoplasm of the neurons.Heterochromatin of nucleus showed little condensed.Seventy two hours after reperfusion,heterochromatin in the pyramidal cells became condensed and dark;the granular neurons had hollowed nuclear membrane and extended partially.Seven days after reperfusion,the nuclear membranes were ruptured and the nuclear fragmentation was displayed in the pyramidal cells.Granular cells showed chromatin condensation into isolated round mass.TUNEL positive pyramidal cells and granular neurons were detected under the electron microscope. CONCLUSION:The separate neuronal populations in the hippocampus were differently vulnerable to ischemic injuries;the CA1 pyramidal neurons were the most vulnerable to the ischemic injury among these neurons.The delayed death in the CA1 pyramidal neurons mainly appeared as necrosis,but the granular neurons in the dentate gyrus appeared as apoptosis like changes.