The Role of Hippocampal area CA2 in Epilepsy

摘要 更深入地了解导致难治性疾病的分子、细胞和电路机制 癫痫对于改进现有的治疗方法至关重要。啮齿动物癫痫模型 为实现这一目标和临床前探索新的治疗方法提供了重要的途径。 在这里，我们关注与人类耐药癫痫障碍相关的两种类型的小鼠模型： 匹罗卡品癫痫持续状态模型和小鼠模型的建立 在导致人类癫痫的电压门控离子通道中存在基因变异。 TLE显示一种称为内侧颞叶的海马神经退行性变的特征模式 硬化症(MTS)，CA1和CA3区锥体神经元大量丢失，相对较少 齿状回(DG)和CA2区。DG和CA2的存活导致了两个都是 对癫痫发作活动很重要。虽然DG在啮齿动物模型中的作用已经得到了很好的研究，但CA2的作用 相对来说还没有被开发出来。在之前的资助期，我们发现PILO-SE导致了 整体的CA2兴奋，由于增加的内在兴奋性，增强突触兴奋来自DG和 减少突触抑制。重要的是，我们发现慢性化学发生或急性闭合环光发生 沉默CA2可显著降低Pilo-SE小鼠的惊厥活动。 然而，我们之前的分析仅限于背侧CA2。我们将在这里讨论腹侧的作用 CA2，因为在人类和啮齿动物模型中的研究表明，腹侧海马区可能是一个更 TLE比背侧海马区是癫痫发作的重要部位。因此，我们将调查这一假设 腹侧CA2化学和/或光遗传沉默在减少癫痫发作方面将比 静息背侧CA2时观察到。我们之前的研究也留下了这样一个问题，即 PILO-SE中CA2兴奋增加与CA2在癫痫发作中的作用有因果关系。我们将解决这一问题 通过询问恢复正常CA2内在兴奋性水平的干预是否可以挽救 PILO-SE中的癫痫发作。这种实验比基于基因的沉默更有优势，因为它们不会 干扰CA2在海马区依赖社会记忆中的正常作用。 除了获得性形式的癫痫外，还发现了越来越多的癫痫病例 由遗传变异引起，一些与MTS有关，另一些没有MTS。在这里，我们解决了 通过研究CA2在癫痫小鼠模型中的作用是否可能在癫痫发作活动中发挥更普遍的作用 由编码HCN1电压门控离子通道的基因突变引起的遗传型癫痫，以及 在该模型中检测CA2沉默是否能抑制癫痫发作。 因此，这一提议的实验为进一步验证CA2作为小说的目标提供了希望 治疗一系列癫痫障碍的治疗方法。

ABSTRACT A deeper understanding of the molecular, cellular, and circuit mechanisms that contribute to intractable epilepsy is of critical importance for improving existing therapeutic approaches. Rodent epilepsy models provide an important approach for achieving this goal and for the preclinical exploration of novel treatments. Here we focus on two types of mouse models relevant to drug-resistant seizure disorders in humans: the pilocarpine status epilepticus model (PILO-SE) of acquired temporal lobe epilepsy (TLE) and a mouse model with a genetic variant in voltage-gated ion channels that cause seizure disorders in humans. TLE shows a characteristic pattern of hippocampal neurodegeneration termed mesial temporal sclerosis (MTS), with substantial loss of pyramidal neurons in the CA1 and CA3 regions and a relative sparing of dentate gyrus (DG) and CA2 regions. Survival of DG and CA2 has led to the hypotheses that both are important for seizure activity. Although the role of DG has been well studied in rodent models, the role of CA2 has remained relatively unexplored. In the previous funding period, we found that PILO-SE leads to increased overall CA2 excitation, due to increased intrinsic excitability, enhanced synaptic excitation from DG and reduced synaptic inhibition. Importantly, we found that chronic chemogenetic or acute closed-loop optogenetic silencing of CA2 led to a significant decrease in seizure activity in PILO-SE mice. However, our previous analyses were restricted to dorsal CA2. We will address here the role of ventral CA2, as studies in both humans and rodent models suggest that ventral hippocampus may be an even more important site for seizures in TLE than dorsal hippocampus. We will therefore investigate the hypothesis that chemogenetic and/or optogenetic silencing of ventral CA2 will be even more effective in reducing seizures than observed upon silencing dorsal CA2. Our previous studies also left open the question as to whether the increase in CA2 excitation in PILO-SE is causally related to the role of CA2 in seizures. We will address this question by asking whether interventions that restore normal levels of CA2 intrinsic excitability can rescue seizures in PILO-SE. Such experiments have the advantage over genetic-based silencing as they will not interfere with the normal role of CA2 in hippocampal-dependent social memory. In addition to acquired forms of epilepsy, an increasing number of cases of epilepsy have been shown to be caused by genetic variants, some associated with MTS and others without MTS. Here we address whether CA2 may play a more general role in seizure activity by investigating its role in a mouse model of a genetic form of epilepsy caused by mutations in the gene encoding the HCN1 voltage-gated ion channel, and testing whether CA2 silencing can suppress seizures in this model. The experiments of this proposal thus offer the promise of further validating CA2 as target for novel therapeutic approaches for treatment of a range of seizure disorders.