Nicotinic acetylcholine receptor function in the mesolimbic dopamine system

项目摘要 长期接触烟草制品中的尼古丁会导致许多健康后果（肺癌， 肺气肿、高血压等）每年有超过600万人因此死亡复发率很高， 那些试图戒烟的人，以及寻求促进戒烟的药物疗法， 适度有效。因此，对于治疗尼古丁的更有效的策略存在显著未满足的需求。 依赖制定这样的战略需要更详细地了解生物 导致尼古丁成瘾的机制。与nAChR机制研究相关的一个基本目标是 更好地了解nAChR在单个神经内离散部位的位置和活性 细胞同样重要的是，我们将这些位置/活动信息与各种神经化学定义的 (e.g.多巴胺、GABA、谷氨酸）细胞类型。对于这些特定的细胞类型， 关于奖励途径，最近的研究指出了一个高度复杂的输入/输出关系。我们确定 nAChR在腹侧被盖区（VTA）的谷氨酸产生神经元中的表达， 表明这些受体使尼古丁或乙酰胆碱介导的突触传递改变 在VTA中。然而，在知识方面仍然存在一些差距，我们将在本项目中解决这些问题。第一次（在 目的1），我们将确定腹侧被盖区谷氨酸神经元内nAChR表现出最大功能的位置 活动这将在大脑神经元的双光子成像期间使用电生理记录来完成 切片这种方法将与使用新型光活化尼古丁的研究相结合，我们最近 介绍直接将这些结构和功能信息联系起来对于充分理解 nAChR调节腹侧被盖区中的谷氨酸传递。在目标2中，我们将回答与nAChR相关的问题 调节VTA内的细胞间通讯。这个核团中的谷氨酸神经元直接撞击 局部DA/GABA神经元，其活性由谷氨酸细胞上的nAChR活性调节。我们将调查 利用光遗传学、光刺激技术和 2-光子显微镜在目标3中，我们将查询移动到行为动物，以确定 目标1-2中研究的成分在动物行为中最重要。使用光纤测光，我们 将在急性尼古丁暴露期间和在获得/表达 尼古丁条件性奖赏行为。为了补充这些实验，我们还将使用化学遗传学， 确定腹侧被盖区谷氨酸神经元是否对尼古丁奖励样行为很重要。通过确定 胆碱能机制如何映射到复杂性（神经化学和连接）的细胞类型， VTA，这个项目将大大推进我们对胆碱能神经传递的理解。这些研究 也可能导致成瘾的新疗法或关于奖励系统功能/活动的新假设。

PROJECT SUMMARY Chronic exposure to nicotine in tobacco products results in numerous health consequences (lung cancer, emphysema, hypertension, etc.) and accounts for over 6 million deaths per year. Relapse rates are high among those who attempt to quit smoking, and pharmacotherapies that seek to foster smoking cessation have moderate effectiveness. Thus, there is a significant unmet need for more effective strategies to treat nicotine dependence. Development of such strategies requires a more detailed understanding of the biological mechanisms leading to nicotine addiction. An essential goal related to mechanistic studies on nAChRs is gaining a better understanding of the location and activity of nAChRs in discrete sites within individual nerve cells. It is also critical that we connect this location/activity information to the various neurochemically-defined (e.g. dopamine, GABA, glutamate) cell types within the brain reward pathways. For these specific cell types in the reward pathway, recent research points to a highly complex input/output relationship. We identified nAChR expression in glutamate-producing neurons in the ventral tegmental area (VTA), and have demonstrated that these receptors enable nicotine- or ACh-mediated alterations in synaptic transmission within the VTA. However, several gaps in knowledge remain, which we will address in this project. First (in Aim 1), we will identify the location within VTA glutamate neurons where nAChRs show the greatest functional activity. This will be done using electrophysiological recordings during 2-photon imaging of neurons in brain slices. This approach will be coupled with studies using a novel photoactivatable nicotine, which we recently introduced. Directly connecting this structural and functional information is critical to fully understanding how nAChRs modulate glutamate transmission in the VTA. In Aim 2, we will answer questions related to nAChR modulation of cell-cell communication within the VTA. Glutamate neurons in this nucleus directly impinge on local DA/GABA neurons, activity which is modulated by nAChR activity on glutamate cells. We will investigate the mechanisms underlying this synaptic communication using optogenetics, photostimulation techniques, and 2-photon microscopy. In Aim 3, we move our queries to the behaving animal to determine which of the components investigated in Aims 1-2 are most important during animal behavior. Using fiber photometry, we will image Ca2+ activity in VTA neurons during acute nicotine exposure and during acquisition/expression of nicotine conditioned reward behavior. To complement these experiments, we will also use chemogenetics to determine whether VTA glutamate neurons are important for nicotine reward-like behavior. By determining how cholinergic mechanisms map onto the complexity (neurochemical and connectivity) of cell types in the VTA, this project will significantly advance our understanding of cholinergic neurotransmission. These studies could also lead to novel treatments for addiction or novel hypotheses about reward system function/activity.