Nicotinic Receptors in Glia-Neuron Interactions

尼古丁成瘾是我们社会中的一个主要健康问题，占医疗保健费用的数百万美元。了解尼古丁作用的一个基本前提是阐明尼古丁乙酰胆碱受体（nAChR）在大脑中的生理作用。最近，已经表明nAChRs在星形胶质细胞中表达。该提案将研究星形胶质细胞nAChRs对小鼠海马CA 3区突触信号传导的作用，以及这些受体如何促进大脑中的胶质细胞-神经元相互作用。该提案将解决两个问题。首先，我们将使用表达与胶质细胞酸性蛋白（GFAP）连接的GFP的小鼠急性海马切片来表征星形胶质细胞中的烟碱信号。将进行电生理学分析，检查星形胶质细胞上的烟碱电流。钙成像将用于阐明这些细胞中钙信号的细节，包括星形胶质细胞内各种钙源的贡献。将检查nAChR诱导的细胞内和细胞间钙波。我们将使用表达由胆碱乙酰转移酶（ChAT）启动子驱动的tau-GFP的转基因小鼠来标记胆碱能轴突。将检查局部刺激胆碱能纤维诱导星形胶质细胞中nAChR电流和钙信号的能力。这些研究将确定星形胶质细胞中功能性nAChR的存在及其响应尼古丁和内源性乙酰胆碱在这些细胞中传递信号的能力。该提案的第二部分将解决一个独特的信号传导，导致海马中苔藓纤维-CA 3突触的动作电位独立形式的传输。我们将研究星形胶质细胞在介导或调节这种形式的短期可塑性的作用，其作用于突触前苔藓纤维终端。这些研究将结合使用电生理学和钙成像。越来越明显的是，成瘾是一个涉及大脑多个区域的享乐稳态问题，而不仅仅是中脑边缘多巴胺能系统。了解nAChR在大脑中的整体作用，以达到一个合理的药物设计，以打击吸烟必须包括这些神经胶质细胞和神经元上的受体的理解。这项建议是朝这个方向的一个开端。公共卫生相关性：已经开发的对抗吸烟的方法是不够的，主要是因为我们缺乏关于这种药物如何影响大脑功能的知识。现在人们认识到，滥用尼古丁等药物对大脑有深远的影响。它们不仅影响大脑中神经细胞的功能，还影响被称为神经胶质的支持细胞。这些支持细胞已被证明在决定神经细胞如何发挥作用方面发挥着非常积极的作用。在这里，我们研究尼古丁对星形胶质细胞（一种神经胶质细胞）的影响，并确定尼古丁如何通过这些细胞影响神经元的功能和信号传导。这项研究将为了解吸烟对大脑的影响开辟新的方向，并有助于开发更好的药理干预措施，以帮助人们打破尼古丁成瘾。

DESCRIPTION (provided by applicant): Nicotine addiction is a major health problem in our society and accounts for millions in health care costs. A fundamental prerequisite for understanding the actions of nicotine is to elucidate the physiological role for nicotinic acetylcholine receptors (nAChRs) in the brain. Recently, it has been shown that nAChRs are expressed in astrocytes. This proposal will examine the role of astrocytic nAChRs on synaptic signaling in the CA3 region of the mouse hippocampus and how these receptors contribute to glia-neuron interactions in the brain. The proposal will address two issues. First, we will characterize nicotinic signaling in astrocytes using acute hippocampal slices from mice expressing GFP linked to the glial fibrillary acidic protein (GFAP). Electrophysiological analyses will be carried out examining nicotinic currents on astrocytes. Calcium imaging will be used to elucidate the details of calcium signaling in these cells, including the contributions from various sources of calcium within astrocytes. nAChR-induced intra- and inter-cellular calcium waves will be examined. We will use transgenic mice that express tau-GFP driven by the cholineacetyl transferase (ChAT) promoter in order to label cholinergic axons. The ability of local stimulation of cholinergic fibers to induce nAChR currents and calcium signals in astrocytes will be examined. These studies will establish the existence of functional nAChRs in astrocytes and their ability to transduce signals in these cells in response to both nicotine and endogenous acetylcholine. The second part of the proposal will address a unique signaling resulting in an action potential- independent form of transmission at the mossy fiber-CA3 synapse in the hippocampus. We will examine the role of astrocytes in mediating or modulating this form of short-term plasticity by its action on the presynaptic mossy fiber terminals. A combination of electrophysiology and calcium imaging will be used in these studies. It is increasingly becoming apparent that addiction is a problem of hedonic homeostasis that involves multiple regions of the brain, not just the mesolimbic dopaminergic system. Understanding the totality of nAChR actions in the brain, in order to arrive at a rational drug design to combat smoking must include the understanding of these receptors on glia as well as neurons. This proposal makes a start in that direction. PUBLIC HEALTH RELEVANCE: Methods that have been developed to combat smoking have been inadequate mainly because of our lack of knowledge on how this drug affects brain functions. It is now being recognized that drugs of abuse like nicotine have far reaching consequences for the brain. They affect not just functions of nerve cells in the brain but also support cells known as glia. These support cells have been shown to play a very active role in determining how the nerve cells function. Here we study the effects of nicotine on astrocytes, a type of glial cells, and determine how nicotine, acting via these cells can affect the functioning of, and signaling by neurons. This study will open a new direction in understanding the consequences of smoking for the brain and aid in the development of better pharmacological interventions to assist people in breaking nicotine addiction.