Role of Cholinergic-Glutamatergic Co-transmission in Forebrain Circuits

描述（由申请人提供）：基底前脑和纹状体胆碱能神经元在大脑功能的许多方面起着关键作用，包括学习和记忆、注意、奖励和运动功能，它们的失调会导致神经精神疾病，如帕金森病、精神分裂症和阿尔茨海默病。几十年来，人们一直认为这些细胞只释放一种经典的递质——乙酰胆碱，然而现在人们知道它们表达囊状谷氨酸转运蛋白3并释放谷氨酸。虽然我们有数据表明纹状体胆碱能神经元中的VGLUT3介导谷氨酸能快速传递并调节胆碱能传递，但对其在基底前脑神经元中的作用及其在这两种人群中的行为作用知之甚少。因此，本基金的目的是确定VGLUT3在前脑胆碱能神经元中的功能和行为作用。在Aim 1中，我们将利用BAC转基因cre重组酶和报告小鼠以及cree依赖性病毒追踪方法，确定VGLUT3在基底前脑核中的细胞分布，并绘制其轴突投影。与传统方法相比，这些新工具具有更高的灵敏度和选择性。在目的2中，我们将确定vglut3介导的基底前脑胆碱能神经元突触信号传导的机制。我们将使用生化方法来评估VGLUT3和VAChT是否驻留在相同的囊泡上，这可能表明协同共包装增加了这些细胞的胆碱能传递。我们将结合膜片钳电生理技术，利用crei依赖性病毒表达的通道视紫红质来检测胆碱能细胞对谷氨酸能的快速传递。在Aim 3中，我们将确定VGLUT3在纹状体和基底前脑胆碱能神经元中的行为作用。使用条件VGLUT3敲除小鼠，我们现在有证据表明胆碱能神经元中与VGLUT3明确相关的行为。这些神经元中转运体的缺失会产生夜间过度运动活动，以及两项工作记忆任务，新手臂识别和自发交替的缺陷。这方面的工作将确定哪一群胆碱能神经元介导这些表型，以及这些细胞的谷氨酸信号传导是否具有行为作用。针对前脑胆碱能神经元信号传导的胆碱组学通常用于治疗许多神经系统疾病。我们在这里的工作表明，这些细胞的谷氨酸信号传导可能提供新的治疗靶点。

DESCRIPTION (provided by applicant): Basal forebrain and striatal cholinergic neurons have a critical role in many aspects of brain function including learning and memory, attention, reward and motor function and their dysregulation contributes to neuropsychiatric disorders such as Parkinson's disease, schizophrenia and Alzheimer's disease. For decades, it was assumed that these cells release only one classical transmitter, acetylcholine, however it is now known that they express the vesicular glutamate transporter 3 and release glutamate. While we have data showing that VGLUT3 in striatal cholinergic neurons mediates fast glutamatergic transmission and modulates cholinergic transmission, not much is known about its role in basal forebrain neurons or its behavioral role in either population. Thus, the goal of this grant is to determine te functional and behavioral role of VGLUT3 in forebrain cholinergic neurons. In Aim 1 we will determine the cellular distribution of VGLUT3 in basal forebrain nuclei and map their axonal projections using our BAC transgenic cre recombinase and reporter mice together with cre-dependent viral tracing methods. These new tools provide higher sensitivity and selectivity over more traditional methods. In Aim 2 we will determine mechanisms of VGLUT3-mediated synaptic signaling by basal forebrain cholinergic neurons. We will use a biochemical approach to assess whether VGLUT3 and VAChT reside on the same vesicles, which would suggest synergistic co-packaging increases cholinergic transmission by those cells. We will use cre-dependent viral expression of channelrhodopsin together with patch clamp electrophysiology to detect fast glutamatergic transmission by cholinergic cells. In Aim 3 we will determine the behavioral role of VGLUT3 in striatal and basal forebrain cholinergic neurons. Using our conditional VGLUT3 knockout mice, we now have evidence of behaviors definitively linked to VGLUT3 in cholinergic neurons. Deletion of the transporter in these neurons produces nocturnal hyperlocomotor activity as well as deficits in two working memory tasks, novel arm recognition and spontaneous alternation. Work in this aim will determine which population of cholinergic neurons mediates these phenotypes and if there is a behavioral role for the glutamate signaling by these cells. Cholinomemetics that target signaling by forebrain cholinergic neurons are commonly used to treat a number of neurological disorders. Our work here suggests that glutamate signaling by these cells could provide novel therapeutic targets.