Role of Cholinergic-Glutamatergic Co-transmission in Forebrain Circuits

描述(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都起着关键作用，包括学习和记忆、注意力、奖励和运动功能，它们的失调会导致神经精神障碍，如帕金森氏症、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，然而现在已经知道，它们表达囊泡谷氨酸转运体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介导了快速的谷氨酸能传递并调节了胆碱能传递，但关于它在基底前脑神经元中的作用或在这两个群体中的行为作用还知之甚少。因此，这项资助的目标是确定VGLUT3在前脑胆碱能神经元中的功能和行为作用。在目标1中，我们将利用我们的BAC转基因cre重组酶和报告小鼠，结合依赖cre的病毒示踪方法，确定VGLUT3在前脑基底核团中的细胞分布，并绘制其轴突投射图。与传统方法相比，这些新工具提供了更高的灵敏度和选择性。在目标2中，我们将确定VGLUT3通过基底前脑胆碱能神经元介导突触信号的机制。我们将使用生化方法来评估VGLUT3和Vacht是否位于相同的囊泡上，这将表明协同联合包装增加了这些细胞的胆碱能传递。我们将使用cre依赖的视紫红质的病毒表达结合膜片钳电生理来检测胆碱能细胞的快速谷氨酸能传递。在目标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。使用我们的条件性VGLUT3基因敲除小鼠，我们现在有证据表明，胆碱能神经元中的行为与VGLUT3明确相关。这些神经元中转运蛋白的缺失会导致夜间的超运动活动，以及两种工作记忆任务的缺陷，即新的手臂识别和自发交替。这一目标的工作将确定哪一组胆碱能神经元调节这些表型，以及这些细胞的谷氨酸信号是否有行为作用。前脑胆碱能神经元靶向信号的胆碱能药物通常用于治疗许多神经疾病。我们在这里的工作表明，这些细胞发出的谷氨酸信号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.