Pathological Mechanisms Of Brain Injury After Seizures In Developing Brains And The Influence Factors

Part INeuronal apoptosis after seizure-induced injury in the immature brainObjective:Apoptosis is a genetically programmed cell death, also called the programmed cell death. This study was designed to observe neuronal apoptosis in cerebral cortex and hippocampus of P10 rats after pentylenetetrazol induced seizures.Methods:Postnatal day 10 (P10) Wistar rats were randomly divided into experimental group and control group; experimental animals were injected with pentylenetetrazol (PTZ) to induced seizures. The control group received saline.24 h after seizure onset, thionin staining was performed to assess the neuronal morphology in the hippocampus and cerebral cortex. TUNEL staining was used to detect cells undergoing apoptosis.Results:1.24 h after seizure onset, we observed single, scattered dead or degenerative neurons in hippocampus and cerebral cortex; 2. TUNEL staining showed increased apoptotic neurons both in hippocampus and cerebral cortex in the experimental group. Apoptotic indexes in hippocampus were (5.24±0.76)% and (1.23±0.31)% in experimental group and control group. Apoptotic indexes in cerebral cortex were (4.93±0.52)% and (1.16±0.27)% in experimental group and control group. Apoptotic indexes in these two positions of experimental group were significantly higher than control group (P＜0.05). There was no significant difference between hippocampus and cerebral cortex of the experimental group.Conclusion:Neuronal apoptosis is increased in hippocampus and cerebral cortex after PTZ-induced seizure in developing rats. There is no significant difference in apoptosis index between hippocampus and cerebral cortex Part IIActivation of autophagy after seizure-induced injury in the immature brainObjective:Autophagy is called type II programmed cell death. It plays an important role in cellular survival, development, and differentiation. It is also involved in stress-induced cellular adaptation. The study is to observe the activation of autophagy in developing rats after PTZ induced seizures.Methods:10-day-old Wistar rats were divided into two groups:experimental group and control group. The experimental group was induced seizure by PTZ. We took the hippocampus and cerebral cortex of rats 2,4,8,16,24,36, and 48 h after seizure onset, and detected the expression of LC3-II, which is a unique marker of the autophagosome in mammalian by Western blot assay; The expressions of LC3 in hippocampus were examined by inmmunofluorescence 24 h after seizure onset.Result:1. In the experimental group, LC3-II/LC3-I are significantly increased from 4 hr in hippocampus and 8 h in the cerebral cortex, peaking at 24 h (P<0.05). The elevation of LC3-II/LC3-I was higher in the hippocampus than in the cerebral cortex (P<0.05).Conclusion:Autophagy is increased in the hippocampus and cerebral cortex of developing rats after PTZ-induced seizures, the activation of autophagy in the hippocampus is higher than the cerebral cortex. PartⅢThe role of autophagy on seizure-induced brain injury in the developing ratsObjective:Autophagy is activated after PTZ induced seizures in developing rats. This study was to investigate the role of autophgy on seizure-induced brain injury in the developing rats and its effect on apoptosis.Methods:10-days-old (P10) Wistar rats were divided into PTZ group,3-MA+PTZ group, 3-MA group and the control group at random.3-MA+PTZ group was pretreated with 3-methyladenine (3-MA) 30 minutes before pentetrazole (PTZ) injection, then the PTZ group and 3-MA+PTZ group were injected PTZ to induce seizures. We took the hippocampi of rats at 24 h after seizure onset, and detected the expression of LC3-Ⅱ, which is a unique marker of the autophagosome in mammalian by Western blot. Apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) method at 24 h after seizure onset.Results:1. The latency was shorter in 3-MA+PTZ group than PTZ group, but the duration of seizure was longer than PTZ group; 2.the relative LC3-Ⅱ/LC3-Ⅰin the hippocampus was significantly higher in PTZ group than control group at 24 h after seizure onset and they were significantly lower in 3-MA+PTZ group than PTZ group; 3. neuronal degeneration and neuronal death in hippocampus of 3-MA+PTZ group were significant than PTZ group, and cell counts in Ammon's horn of 3-MA+PTZ group was less than PTZ group; 4. the apoptotic indexes in 3-MA+PTZ group, PTZ group,3-MA group and control group were (21.26±2.34)%, (5.58±0.63)%, (0.86±0.17)%, and (0.97±0.25)%, respectively, as well as the apoptotic index of 3-MA+PTZ group was significantly higher than PTZ group (P <0.05).Conclusion:Activation of autophagy inhibits apoptosis and plays a protective role on brain of developing rats after PTZ induced seizures.