Interactions Among Hippocampal Interneuron Circuits

项目描述（申请人提供）：本项目的主要假设：内源性阿片、大麻素和CCK系统通过海马中间神经元相互作用，共同调节锥体细胞的兴奋性。低频神经元群振荡（特别是4-12赫兹的θ“？”和30-80赫兹的伽马“？”）代表了对高阶认知处理至关重要的大脑状态。gaba能篮细胞微电路的活性对于几种形式的节律产生是必需的，然而关于潜在的细胞机制的许多问题尚未解决，主要是因为现有的工具不足以选择性地研究稀疏和广泛分散的细胞电路。被称为低频振荡（LFOs）的模型现象，捕捉了体内更为复杂的大脑节律的一些特性。本应用将利用新的光遗传学方法在微电路水平上解决lfo的机制问题。目的是阐明可能有助于阐明体内现象的基本细胞回路特性。分子生物学工具将通过病毒载体将光敏分子（“视蛋白”）引入目标细胞群。载体包含一个双柔的、倒置的融合蛋白基因，融合蛋白由一个视蛋白和一个荧光标记蛋白组成。在细胞特异性启动子的控制下，将载体导入表达cre -重组酶的转基因小鼠脑内。我们将视蛋白靶向海马中表达小白蛋白（PV）或表达胆固醇收缩素（CCK）的中间神经元，或内侧隔膜中表达乙酰胆碱（ACh）的细胞。视蛋白的分子特性不同，特定视蛋白的光激活会激发或抑制表达它的细胞。我们将使用激动剂

DESCRIPTION (provided by applicant): Major hypothesis of this project: The endogenous opioid, cannabinoid, and CCK systems mutually interact via hippocampal interneurons and thereby jointly regulate the excitability of pyramidal cells. Low frequency neuronal population oscillations (especially theta "?", 4-12 Hz, and gamma "?", 30-80 Hz, rhythms) represent brain states that are crucial for high order cognitive processing. Activity in GABAergic basket cell microcircuits is required for several forms of rhythm generation, yet many questions regarding the underlying cellular mechanisms are unresolved, largely because available tools are inadequate for selectively investigating the sparse and widely dispersed cellular circuits. Model phenomena, called low frequency oscillations (LFOs), capture some of the properties of the much more complex in vivo brain rhythms. The present application will use new optogenetic methods to address questions about mechanisms of LFOs at the microcircuit level. The goal is to elucidate fundamental cell circuit properties that may help illuminate the in vivo phenomena. Molecular biological tools will be used to introduce light-sensitive molecules ("opsins") into targeted cell groups via viral vectors. The vectors contain a double-floxed, inverted gene for a fusion protein consisting of an opsin plus a fluorescent marker protein. Vectors are introduced into the brains of transgenic mice expressing Cre-recombinase under the control of cell-specific promoters. We will target the opsins to either the parvalbumin (PV) - expressing, or cholescystokinin (CCK) - expressing interneurons in hippocampus, or acetylcholine (ACh) - expressing cells in the medial septum. Depending on its molecular properties, light-activation of a particular opsin will either excite or inhibit the cell expressing it. We will use the excitatory opsin, Channelrhodopsin2, and the inhibitory opsin, Halorhodopsin in the proposed experiments. Flashes of light of an appropriate wavelength will either excite or inhibit defined networks of cells, even though the cells are scattered in the tissue. Optogenetic methods will complement high resolution electrophysiological analysis of individual neurons. In the hippocampus, the mu-opioid receptor, ?OR, or the cannabinoid receptor, CB1R, are segregated at high density on the PV or CCK cells, respectively. We will ask how the individual microcircuits regulated by ?ORs and CB1Rs interact to foster inhibitory LFOs. The Specific Aims are to: Aim #1: Test the hypothesis that CCK and PV cells mutually influence each other. Aim #2: Test the hypothesis that CCK and PV cell IPSPs collectively generate LFO-LFPs. Aim #3: Test the hypothesis that LFO-IPSCs and LFO-LFPs can be triggered by endogenous ACh. PUBLIC HEALTH RELEVANCE: Health Relevance: Disordered function of inhibitory microcircuits has been implicated in psychiatric disorders such as schizophrenia, autism, and Alzheimer's Disease, among others. In addition, opiate and cannabinoid drugs have actions that interact in affecting behavior, and yet the ways in which they interact is not known. A detailed understanding of the cross-talk between PV and CCK cell microcircuits will impact on important neurological problems.