Modulation of Neocortical Interneuronal Function

描述（由申请人提供）：控制大脑皮层中兴奋性和抑制性突触传递的突触前机制在正常信息处理中具有关键作用，并且还可能导致各种脑部疾病（如认知能力下降和癫痫）的病理生理学。拟议的实验主要集中在抑制性突触传递介导的γ-氨基丁酸（GABA）含有快速尖峰（FS）抑制性中间神经元和其调制的活动的钠-钾ATP酶（NKA，钠泵）。FS中间神经元介导最常见和最强的抑制形式，并且已知易受损伤。初步数据显示，在部分分离的（底切或UC）新皮层中，α 3 KA（中间神经元中的主要泵亚型）的免疫反应性在FS细胞的轴突终末中降低。我们将检验以下假设：FS向兴奋性细胞GABA能的传递将受到α 3 KA活性降低的影响，无论是通过强心类固醇治疗发生在部分分离的致癫痫皮质，还是发生在NKA α 3亚基基因改变的癫痫小鼠中。具体的目的是1）评估强心类固醇或皮质损伤对泵电流的影响和FS对兴奋性细胞抑制的动力学; 2）研究增强损伤或损伤的皮质中α 3 KA表达的功能效应。 Myshkin小鼠皮质与小分子部分TrkB激动剂;和3）检验以下假设：在具有遗传诱导癫痫的Myshkin小鼠中，由于α3泵亚基突变，FS GABA能神经元的性质和FS细胞的传递将被选择性改变。技术将包括在皮质切片中配对记录以获得FS细胞选择性产生的单一（u）突触后电流（IPSC）;在小白蛋白/ChR 2小鼠中选择性激活FS细胞的光遗传学方法;以及激光扫描光刺激和多个同时细胞外记录以监测效应网络效应。部分皮层隔离模型将用于提供慢性损伤的致癫痫切片，并评估可能导致过度兴奋的泵功能变化。目的是确定影响GABA能传递的泵活性、损伤诱导的异常或可能导致过度兴奋和癫痫发生的泵功能遗传改变;并测试增强NKA表达是否会挽救UC皮质中受损的FS细胞介导的抑制。

DESCRIPTION (provided by applicant): Presynaptic mechanisms controlling excitatory and inhibitory synaptic transmission in the cerebral cortex have critical roles in normal information processing and also may contribute to the pathophysiology of a variety of brain disorders such as cognitive decline and epilepsy. The proposed experiments focus primarily on inhibitory synaptic transmission mediated by gamma amino butyric acid (GABA)-containing fast-spiking (FS) inhibitory interneurons and its modulation by activities of sodium-potassium ATPase (NKA, the sodium pump). FS interneurons mediate the most common and strongest form of inhibition and are known to be vulnerable to injury. Preliminary data show that immunoreactivity for α3KA, the main pump isoform in interneurons, is decreased in axonal terminals of FS cells in partially isolated (undercut or UC) neocortex. We will test the hypothesis that FS to excitatory cell GABAergic transmission will be compromised by decreases in α3KA activity, whether it occurs in partially isolated epileptogenic cortex, via treatment with cardiotonic steroids, or in epileptic mice with genetically altered NKA alpha3 subunit. Specific aims are to 1) assess effects of cardiotonic steroids or cortical injury on pump current and the dynamics of FS to excitatory cell inhibition; 2) study functional effects of enhancing α3KA expression in injured or Myshkin mouse cortex with a small molecule partial TrkB agonist; and 3) test the hypothesis that properties of FS GABAergic neurons and transmission from FS cells will be selectively altered in Myshkin mice with a genetically induced epilepsy due to mutations in the α3 pump subunit. Techniques will include paired recordings in cortical slices to obtain unitary (u) inhibitry postsynaptic currents (IPSCs) generated selectively by FS cells; optogenetic approaches in parvalbumin/ChR2 mice to selectively activate FS cells; and both laser scanning photostimulation and multiple simultaneous extracellular recordings to monitor effects network effects. The partial cortical isolation model will be used to provide chronically injured, epileptogenic slices and assess changes in pump function that might contribute to hyperexcitability. The goals are to identify pump activities that influence GABAergic transmission, abnormalities induced by injury or genetic alterations in pump function that may contribute to hyperexcitability and epileptogenesis; and test whether enhancing NKA expression will rescue compromised FS cell-mediated inhibition in the UC cortex.