| Epilepsy is a type of heterogeneous disease caused by hyper synchronized discharges generated by excited neurons. Mesial temporal lobe epilepsy (MTLE) is one of the most common epilepsy syndromes and the most common intractable epilepsy in adults. Hippocampal sclerosis (HS) is frequently seen in MTLE, characterized by proliferation of astrocytes, loss of neurons, dispersion of granule cells, and mossy fiber sprouting in hippocampus. However, the molecular mechanism of hippocampal sclerosis and pathogenesis of MTLE is still unclear. During the past decade, Notchl signaling pathway has been found responsible for pathological phenomenon presented in or similar to those in hippocampal sclerosis. Meanwhile, researches indicate that Notchl signaling pathway takes part in neurogenesis following injuries including status epilepticus, and can be activated in response to neuronal activity. Moreover, researchers find that the critical component of Notchl signaling pathway, NICD1, is increased during epileptogenesis in the animal model of HS-MTLE, and there were similar findings in the sclerotic hippocampi of MTLE patients underwent surgery. Thus, it is important to uncover the roll of Notchl signaling pathway in the pathogenesis of hippocampal sclerosis and MTLE.ObjectiveTo discover whether the activation of Notchl signaling pathway is related to the development of HS-MTLE or not, and if it promotes spontaneous seizures during the chronic phase of epilepsy.Methods1. Implant a depth electrode and drug-adding device in the right hippocampus of each of the experiment C57BL/6mouse. Inject Jaggedl to activate Notchl pathway(BSA control) or DAPT to inhibit the pathway(DMSO control) via the device before injecting in the right hippocampus(r. i. h.)7ng kainic acid to induce the acute model of HS-MTLE. Monitoring video-electroencephalogram (vEEG), and calculate the respective seizure parameters after activation or inhibition of the pathway. Induce another group of mice with200ng kainic acid (r. i. h) to build chronic model of HS-MTLE and implant them with the same device. After confirming stable baselines of time in seizure by vEEG monitoring, they were injected with Jaggedl (r. i. h.) to determine its effect on the time of seizure during a certain period of time. Inject DAPT+Jaggedl (r. i. h) on the same mice after a washout period, and calculating the time of seizure after de-activating the pathway.2. Identify the distribution of Notchl by immunofluorescence in the hippocampus in the chronic phase (5w) of200ng kainic acid mouse model.Results1. Normal mouse EEG shows5-7Hz θ background. Both acute and chronic model show high voltage sharp waves, paroxysmal hippocampal discharge, and discharges propagating to cerebral cortex. In addition, acute model shows paroxysmal spike-and-wave or poly spike-and-wave, high voltage spikes buildup and status epilepticus.2. In chronic model, time in seizure was significantly reduced after Jaggedl injection (n=5, p=0.00014versus baseline by repeated measures ANOVA followed by Dunnet’s test), but without much change after DAPT+Jaggedl injection (n=2).3. In acute model, time in ictal activity (p=0.0048) and number of ictal activity (p=0.0109) were significantly increased after Jaggedl injection versus control by Mann-Whitney’s test (n=6or10). Time in ictal activity (p=0.009) and number of ictal activity (p=0.0111) were significantly reduced versus control by the same test (n=7).4. Excessive activation of Notchl is seen in the hippocampus of5w mouse model, mainly located in the dentate gyrus.Conclusion1. The model of intrahippocampal electrode and drug adding device was successfully built.2. Notchl signaling pathway promotes epileptiform discharges and seizures in acute model of HS-MTLE, but suppresses spontaneous seizures in chronic model, indicating its different effects on the development and progression of HS-MTLE. 3. Notchl is activated within dentate gyrus in chronic phases of HS-MTLE model. |
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