Nicotinic acetylcholine receptor function in the mesolimbic dopamine system

项目总结 长期接触烟草产品中的尼古丁会导致许多健康后果(肺癌， 肺气肿、高血压等)每年造成600多万人死亡。复发率很高，在 那些试图戒烟的人和寻求促进戒烟的药物疗法 效果适中。因此，对治疗尼古丁的更有效策略的需求还远远没有得到满足。 依赖。发展这样的策略需要对生物学的更详细的理解 导致尼古丁成瘾的机制。与nAChRs机制研究相关的一个基本目标是 更好地了解nAChRs在单个神经内不同部位的位置和活性 细胞。同样重要的是，我们将这种位置/活动信息与各种神经化学定义的 (例如，多巴胺、GABA、谷氨酸)在大脑奖赏通路中的细胞类型。中的这些特定单元格类型 最近的研究指出，奖励途径是一种高度复杂的输入/输出关系。我们确认了 NAChR在腹侧被盖区(VTA)产生谷氨酸的神经元中的表达，并 证明这些受体能够使尼古丁或ACh介导的突触传递改变 在VTA内。然而，知识中的几个差距仍然存在，我们将在这个项目中解决这一问题。第一个(在 目的1)，我们将确定在VTA谷氨酸神经元中nAChRs显示最大功能的位置 活动。这将使用双光子脑神经元成像期间的电生理记录来完成 切片。这一方法将与使用一种新的可光激活尼古丁的研究相结合，我们最近 介绍。直接连接这些结构和功能信息对于充分理解 NAChRs调节VTA内谷氨酸的传递。在目标2中，我们将回答与nAChR相关的问题 VTA内小区间通信的调制。这个核团中的谷氨酸神经元直接撞击 局部DA/GABA神经元，其活动受谷氨酸细胞上nAChR活性的调节。我们会调查的 利用光遗传学、光刺激技术和 双光子显微镜。在目标3中，我们将我们的问题移到行为良好的动物身上，以确定 AIMS 1-2中研究的成分在动物行为中是最重要的。使用光纤光度法，我们 将成像在急性尼古丁暴露期间和在获得/表达期间VTA神经元的钙活性 尼古丁制约了奖赏行为。为了补充这些实验，我们还将使用化学遗传学来 确定VTA谷氨酸神经元对尼古丁奖赏样行为是否重要。通过确定 胆碱能机制如何映射到细胞类型的复杂性(神经化学和连接性) VTA，这个项目将极大地促进我们对胆碱能神经传递的理解。这些研究 也可能导致针对成瘾的新疗法或关于奖励系统功能/活动的新假说。

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.