Glycine Channels and Hippocampal Excitability

士的宁敏感的甘氨酸门控氯离子通道（GlyR）在大脑中的抑制作用在很大程度上被忽视，尽管这些受体在整个中枢神经系统的表达。有趣的是，在一些癫痫动物模型中，增加脑脊液（CSF）中的甘氨酸水平抑制海马和皮层中的重复神经元放电，暗示GlyRs在调节神经元兴奋性中的重要功能。GlyR在海马体中表达，海马体是一个高度依赖于有效神经元抑制以实现正常功能的脑区域，然而，这些受体的生理作用根本未知。该提议的主要假设是，在海马中，GlyR的激活提供了一种未描述的基本抑制机制，该机制通过直接激活突触后受体来抑制兴奋性锥体细胞和抑制性中间神经元的活性，此外，GlyR激活通过抑制突触传递来限制神经元网络的功能。这项建议的长期目标是建立一个新的作用，在海马GlyR和了解介导的影响GlyR激活神经元活动的细胞机制。锥体细胞的细胞外脉冲记录以及大鼠海马切片中锥体细胞和中间神经元的全细胞和穿孔贴片记录将与药理学工具相结合，以检查整个发育过程中海马中突触后GlyR的功能表达，并确定这些受体的激活如何影响突触网络。我们将认真对待以下具体目标：1）为了检验以下假设：锥体细胞和中间神经元的功能性GlyR表达在整个发育过程中持续，并且由这两种细胞类型表达的GlyR的生理学和药理学性质是相同的，以及2）为了检验以下假设：GlyR激活通过突触后-突触--突触-突触--介导的传播抑制。在这项研究中使用的海马切片制备的优势，允许直接甘氨酸对个别神经元和突触回路的影响，以检查在一个良好的表征系统，其中记录的神经元保持在其天然的突触环境。我们的方法预计将产生新的信息，这将为GlyRs抑制作用的新研究领域铺平道路。此外，预计本研究的结果将为预防癫痫发作活动的新型治疗策略的设计提供见解。

An inhibitory role of strychnine-sensitive glycine-gated chloride channels (GlyRs) in the brain has largely been ignored, despite the known expression of these receptors throughout the CNS. Interestingly, in some animal models of epilepsy, increasing the glycine levels in cerebral spinal fluid (CSF) depresses repetitive neuronal firing in hippocampus and cortex, implicated an important function of GlyRs in modulating neuronal excitability. GlyRs are expressed in hippocampus, a brain region highly dependent upon effective neuronal inhibition for normal function, however, the physiological role of these receptors is simply not known. The major hypothesis of this proposal is that in hippocampus, activation of GlyRs provides an undescribed, fundamental inhibitory mechanism that depresses the activity of excitatory pyramidal cells and inhibitory interneurons via direct activation of post-synaptic receptors and furthermore, that GlyR activation limits the of the neuronal network by depressing synaptic transmission. The long-term goal of this proposal is to establish a new role for GlyRs in hippocampus and to understand the cellular mechanisms mediating the effects of GlyR activation on neuronal activity. Extracellular popspike recordings of pyramidal cells and whole-cell and perforated patch recordings of pyramidal cells and interneurons in rat hippocampal slices will be combined with pharmacological tools to examined the functional expression of post- synaptic GlyRs in hippocampus throughout development and determine how activation of these receptors affects the synaptic network. We will carefully address the following Specific Aims: 1) To test the hypothesis that functional GlyR expression by pyramidal cells and interneurons continues throughout development and that the physiological and pharmacological properties of GlyRs expressed by these two cell types are the same and 2) To test the hypothesis that GlyR activation limits the activity of the synaptic network under basal and hyperexcitable conditions through a post-synaptically-mediated depression of transmission. The use of the hippocampal slice preparation in this study has the advantage of allowing direct glycine effects on individual neurons and synaptic circuits to be examined in a well-characterized system, where recorded neurons remain in their native synaptic environment. Our approach is anticipated to yield novel information that will pave the way for a new area of investigation into the inhibitory role of GlyRs. Furthermore, it is expected that the results from this study will provide insight into the design of novel therapeutic strategies for the prevention of seizure activity.