Respiration and Generalized Epilepsies

项目摘要 棘波放电(SWDS)是遗传性全身性癫痫(GGES)中常见的癫痫发作类型。 过度换气在绝大多数失神癫痫患者中触发SWDS，最多的是 儿科GGE的常见形式。我们最近开发了一种啮齿动物癫痫模型，在这种模型中，我们可以诱发一种 换气过多的SWD暴发。在过度换气的6分钟内，社会福利署的数量增加了500%以上。 我们现在利用这一模式，以前所未有的方式获得相关的核心癫痫产生机制 带着SWDS。 通过结合单个动物的体积描记、脑电和血液测量，我们发现SWD循环 似乎对血液的酸碱度非常敏感。首先，我们证明了缺氧，一种激活过度换气的条件， 强烈地唤起了啮齿动物SWD。低氧诱导的过度换气导致二氧化碳呼出增加和 伴随的血液碱化(即呼吸性碱中毒)。我们还表明，低氧引起的SWD 当大气中的二氧化碳升高时，就会被废除，从而支持血液碱化驱动的假设 过度换气--诱发SWD。最后，我们还证明了过度换气的光遗传激活 正常大气条件-一种降低血液二氧化碳但增加氧气的实验程序-也 唤起了SWD的注意。因此，总的来说，我们的数据显示，SWD似乎主要与血液中的二氧化碳存在相关性。 我们用脑切片电生理学和钙成像来补充我们的体积描记-脑电数据。我们 将我们的注意力集中在丘脑层内核上，因为活动依赖细胞标记 在低氧诱导的过度换气后，方法(即CFO)一致地标记该区域内的细胞。通过使用 全细胞膜片钳记录技术我们证明了丘脑层内细胞产生 在碱化条件下使离子电流去极化。这股电流的很大一部分似乎是由 通过增强兴奋性突触驱动。 有了我们的初步数据，我们现在提出一个项目，旨在测试激活 急性呼吸性碱中毒引起的丘脑层内pH敏感神经元缺失 癫痫发作。识别这些神经元及其激活机制将有助于制定新的治疗策略。 最常见的儿科GGES是一种只有几十年历史的次佳治疗方法。我们 具体检验以下主要假设： Aim 1呼吸性碱中毒引发失神发作。 目标2自发性和过度换气触发的癫痫使用相同的神经电路。 完成后，我们希望项目的结果将提供对基本知识的重要的、新的见解 细胞和电路级的机制，驱动普遍的尖峰波放电，因此铺平了新的 全面性癫痫治疗的途径。

Project Summary Spike-Wave Discharges (SWDs) are a common type of seizure in the Genetic Generalized Epilepsies (GGEs). Hyperventilation triggers SWDs in the overwhelming majority of patients with absence epilepsy, the most common form of pediatric GGE. We have recently developed a rodent epilepsy model wherein we can evoke a burst of SWDs with hyperventilation. Within 6 minutes of hyperventilation, SWD count increases by over 500%. We now leverage this model to gain unprecedented access to core seizure-generating mechanisms associated with SWDs. By combining plethysmography, EEG and blood measurements in single animals, we show that SWD circuits appear critically sensitive to blood pH. First, we show that hypoxia, a condition that activates hyperventilation, robustly evokes rodent SWDs. Hypoxia-induced hyperventilation results in increased exhalation of CO2 and concomitant blood alkalization (i.e. respiratory alkalosis). We also show that hypoxia-evoked SWDs are abolished when atmospheric CO2 is elevated, thereby supporting the hypothesis that blood alkalization drives hyperventilation-evoked SWDs. Finally, we also show that optogenetic activation of hyperventilation during normal atmospheric conditions – an experimental procedure that reduces blood CO2 but increases O2 – also evokes SWDs. Thus, collectively our data show that SWDs appear to primarily covary with blood CO2. We complement our plethysmography-EEG data with brain slice electrophysiology and calcium imaging. We focus our attention on the intralaminar nuclei of the thalamus because activity-dependent cell tagging approaches (i.e. cFos) consistently label cells within this region after hypoxia-induced hyperventilation. By using whole-cell patch clamp recording techniques we demonstrate that intralaminar thalamic cells produce depolarizing ionic currents during alkalized conditions. A significant portion of this current appears to be mediated by enhanced excitatory synaptic drive. With our preliminary data, we now present a project that aims to test the overarching hypothesis that activation of pH-sensitive intralaminar thalamic neurons by acute respiratory alkalosis precipitates absence seizures. Identifying these neurons and their mechanisms of activation will inform new strategies to treat the most common pediatric GGEs, disorders for which only decades-old, sub-optimal treatments exist. We specifically test the following main hypotheses:  Aim 1 Respiratory alkalosis triggers absence seizures.  Aim 2 Spontaneous and hyperventilation-triggered seizures utilize the same neural ciruitry. When complete, we expect that the results of our project will provide significant, new insights into fundamental cellular- and circuit-level mechanisms that drive generalized spike-wave discharges, and therefore pave new avenues for generalized epilepsy treatments.