The Role of Astroglia in Brain State-Dependent Neural Activity

清醒行为伴随着警觉性的波动，塑造大脑的整体活动状态，以 优化细胞和电路活动。这种脑状态依赖的细胞和分子机制 神经活动的调节还没有被很好地理解。使用我们最近开发的一种老鼠移动模式 研究发现，从静息状态到主动运动的转变与大脑中 神经递质去甲肾上腺素和导致星形胶质细胞的钙激活。星形胶质细胞被激活 同时，在小脑和初级视觉皮质等不同的大脑区域，表明它们 可能在调节全局大脑状态依赖的神经活动调节方面发挥重要作用。精准的 运动性星形胶质细胞钙激活的分子机制及其影响 成人大脑中的神经元活动尚不清楚。在这个项目中，我们将检验运动的假设-- 诱导去甲肾上腺素对神经元活动的调节是由星形胶质细胞介导的。我们将应用组合 体内双光子钙离子成像和电生理以及特定小鼠的急性切片实验 已经以特定细胞类型的方式进行基因改造的品系，以揭示细胞和分子 星形胶质细胞介导的、脑状态依赖的神经调节机制。我们的研究重点将是 在小脑皮质上，利用一个仅由少数细胞组成的回路。一种新的应用 一种特定的Cre鼠系将使我们能够有选择地操纵Bergmann胶质细胞，同时离开Vlaate 小脑皮质的星形胶质细胞没有受到干扰。我们将追求以下目标：(1)结合 我们将用全局和细胞类型特异的基因敲除小鼠进行免疫细胞化学和功能研究 确定运动诱导的Bergmann胶质细胞钙激活所需的受体的身份和位置。 (2)我们将研究运动诱导的浦肯野神经元的钙离子和电信号。 小脑皮层的神经元。利用Bergmann glia全球钙升高的遗传消除，我们将 分离运动诱导的浦肯野神经元信号成分是由先前的Bergmann胶质引起的 钙离子被激活。(3)在切片实验和体内实验中结合药理学和细胞类型特异性基因敲除， 我们将剖析小脑星形胶质细胞影响主要神经元活性依赖的分子机制。 关于行为状态的信息。小脑Bergmann胶质细胞与绒毛星形胶质细胞有许多共同的功能特性 大脑的其余部分，包括运动诱导的、依赖去甲肾上腺素的全局钙激活。 因此，我们预计我们的机制研究将对理解星形胶质细胞的作用具有指导意义。 在大脑中，依赖于状态的去甲肾上腺素能神经调节整个大脑。这项工作将建立 为进一步研究退行性脑损伤下脑状态依赖的神经信号转导机制奠定基础 与去甲肾上腺素能信号变化相关的神经行为状况，如阿尔茨海默病， 帕金森氏症和自闭症。

Awake behavior is accompanied by fluctuations in vigilance shaping the overall activity state of the brain to optimize cellular and circuit activity. The cellular and molecular mechanisms for such brain state-dependent adjustments in neural activity are not well understood. Using a mouse locomotion paradigm we have recently found that the transition from a resting state to active locomotion is associated with release of the neurotransmitter norepinephrine and leads to Ca2+ activation of astroglia. Astroglia are activated simultaneously in brain regions as disparate as the cerebellum and primary visual cortex suggesting that they might play a major role in mediating global brain state-dependent modulation of neural activity. The precise molecular mechanism of locomotion-induced astroglia Ca2+ activation as well as the consequences for neuronal activity in the adult brain are not known. In this project we will test the hypothesis that locomotion- induced noradrenergic modulation of neuronal activity is mediated by astroglia. We will apply a combination of in vivo two-photon Ca2+ imaging and electrophysiology, and acute slice experiments on specific mouse lines that have been genetically modified in a cell type-specific manner, to reveal the cellular and molecular mechanisms of astroglia-mediated, brain state-dependent neuromodulation. The focus of our studies will be on the cerebellar cortex leveraging on a circuit that consists only of a handful of cells. A novel application of a specific Cre mouse line will enable us to selectively manipulate Bergmann glia while leaving velate astrocytes of the cerebellar cortex unperturbed. We will pursue the following aims: (1) Combining immunocytochemistry and functional studies with global and cell type-specific knockout mice we will determine identity and location of receptors required for locomotion-induced Bergmann glia Ca2+ activation. (2) We will investigate locomotion-induced Ca2+ and electrical signals in Purkinje neurons, the principal neurons of the cerebellar cortex. Using genetic elimination of Bergmann glia global Ca2+ elevations we will isolate components of locomotion-induced Purkinje neuron signaling that are caused by prior Bergmann glia Ca2+ activation. (3) Combining pharmacology and cell type-specific knockout in slice experiments and in vivo, we will dissect the molecular mechanism how cerebellar astroglia impact principal neuron activity dependent on the behavioral state. Cerebellar Bergmann glia share many functional properties with velate astrocytes in the remainder of the brain, including locomotion-induced, norepinephrine-dependent global Ca2+ activation. Therefore, we anticipate that our mechanistic studies will be instructive for understanding the role of astroglia in brain state-dependent noradrenergic neuromodulation throughout the brain. This body of work will build the groundwork for future studies on brain state-dependent neural signaling under neurodegenerative and neurobehavioral conditions associated with changes in noradrenergic signaling, such as Alzheimer's disease, Parkinson's disease and autism.