Role of metabotropic glutamate receptor expression in nicotine dependence

 说明(申请人提供)：尼古丁依赖，以吸烟的形式，是全世界可预防的发病率和死亡率的主要来源。尽管目前有可用的治疗干预措施，但成功戒烟率仍然很低。因此，迫切需要开发新的、更有效的治疗方法。越来越多的证据表明，兴奋性谷氨酸传递在调节尼古丁增强的中皮质边缘系统中起着关键作用，这表明谷氨酸受体可能是治疗尼古丁成瘾的创新靶点。通过激活突触前抑制性代谢性谷氨酸受体2/3(mGluR2/3)来减少谷氨酸的传递，从而减弱尼古丁的摄取和寻找。然而，由于缺乏亚型选择性的药理学工具，每个受体(2和3)在尼古丁依赖中的相对作用尚不清楚。此外，关于抑制性突触前mGluR7在尼古丁中的作用还知之甚少 依赖。唯一商业化的mGluR7激动剂AMN082远远不是最理想的，因为它的代谢物产生了非靶点效应。该项目旨在开发分子工具，使这三种mGluR亚型在特定的大脑部位能够特异性地过度表达，从而使我们能够调查这些受体中的每一种在尼古丁依赖中的作用。慢病毒介导的遗传操作允许基因有效地转移到大脑中，并维持对目标受体的长期调节(S)。这种有针对性的实验方法使人们能够探索尼古丁依赖的机制基础。在特定目标1下的工作将产生和验证病毒载体，以在腹侧被盖区(VTA)的谷氨酸末端过表达mGluR2、3和7，腹侧被盖区是中脑边缘系统中的一个大脑部位，与尼古丁依赖密切相关，并且这些受体的密度很高。我们将构建神经元非特异性病毒载体，并在体外进行验证，以检测载体表达的mGluRs介导的功能。谷氨酸能神经元特异性载体也将被产生。所有载体都将在体内得到验证，以检测载体诱导的大鼠脑内蛋白质和mRNA水平的表达和变化。具体目标2将利用这些分子工具开始研究每一种mGluR在尼古丁增强和激励作用中的作用。具体地说，病毒载体将被注入VTA，之后将进行尼古丁自我给药。我们假设mGluR2、3或7的过表达将减弱尼古丁的自我给药。综上所述，本项目将提供新的分子工具，并启动这些工具在 用成熟的行为大鼠程序研究mGluR亚型与尼古丁依赖的关系。这项工作的发现将为未来的R01 NIH拨款申请提供基础，该申请将系统地探索这些mGluR在尼古丁依赖的不同方面的作用。

 DESCRIPTION (provided by applicant): Nicotine dependence, in the form of tobacco smoking, is a major source of preventable morbidity and mortality worldwide. Despite the currently available therapeutic interventions, successful smoking quit rates remain low. Thus, there is an urgent need to develop new and more efficacious treatments. Accumulating evidence suggests a crucial role of excitatory glutamate transmission in the mesocorticolimbic system in mediating nicotine reinforcement, suggesting that glutamate receptors may be innovative targets for the treatment of nicotine addiction. Decreasing glutamate transmission by activation of the presynaptic inhibitory metabotropic glutamate receptor 2/3 (mGluR2/3) attenuates nicotine taking and seeking. However the relative contribution of each receptor (2 vs 3) in nicotine dependence is unknown due to the lack of subtype selective pharmacological tools. Further, little is known regarding the role of the inhibitory presynaptic mGluR7 in nicotine dependence. The only commercially available mGluR7 agonist, AMN082, is far from optimal because of the off-target effects produced by its metabolite. This project seeks to develop the molecular tools that will enable the cell-specific overexpression of these three mGluR subtypes in specific brain sites to allow us to investigate the role of each one of these receptors in nicotine dependence. Lentivirus-mediated genetic manipulations permit the efficient transfer of genes into the brain and sustain long-term regulation of the target receptor(s). This targeted experimental approach allows one to probe the mechanistic basis of nicotine dependence. Work under Specific Aim 1 will generate and validate viral vectors to overexpress mGluR2, 3 and 7 on glutamate terminals in the ventral tegmental area (VTA), a brain site within the mesolimbic system that is critically involved in nicotine dependence and where there is high density of these receptors. Neuron non-specific viral vectors will be generated and validated in vitro to examine the function mediated by vector-expressed mGluRs. Glutamatergic neuron-specific vectors will also be generated. All the vectors will be validated in vivo to examine vector-induced expressions and changes of protein and mRNA levels in the rat brain. Specific Aim 2 will initiate work towards the investigation of the role of each mGluR in the reinforcing and motivational effects of nicotine by using these molecular tools. Specifically, viral vectors will be injected ino the VTA, after which nicotine self-administration will be conducted. We hypothesize that overexpression of mGluR2, 3 or 7 will attenuate nicotine self-administration. In summary, this project will provide novel molecular tools, and then initiate the application of these tools in the investigation of the involvement of mGluR subtypes in nicotine dependence using well-established behavioral rat procedures. Findings from this work will provide the foundation for a future R01 NIH grant application that will systematically explore the role of these mGluRs in different aspects of nicotine dependence.