Metabotropic Glutamate Regulation of Amphetamine Action

描述（由申请人提供）：谷氨酸是大脑中的一种主要神经递质，其在药物成瘾中的作用仍然是旨在揭示滥用药物成瘾特性的神经化学机制的动物研究中的热门话题。该实验室长期以来一直支持研究代谢型谷氨酸受体（mGluRs）的作用。在最后一个时期的补助金，我们已经确定，第一组mGluR（mGluR 1和5亚型），在纹状体密集表达的药物作用的关键调节。具体地，急性施用的精神兴奋剂安非他明（AMPH）需要I组mGluR的活化以增强大鼠纹状体神经元中的内源性强啡肽活性，这是被认为能稳态抑制药物作用的关键反应。长期行为可塑性的一种形式，对大鼠重复注射AMPH的行为敏感化，是一种广泛使用的动物模型，因为它模仿了人类成瘾者对药物渴望的加剧。有趣的是，我们最近发现，反复AMPH管理显着减少组I mGluR mRNA和蛋白质在纹状体。这提出了一个创新的问题，是否重复注射AMPH可以逐步下调组I mGluR的表达，从而激活抑制性强啡肽的功能，从而诱导行为敏化。因此，在该延续提案中，提出了一系列实验来评估总体假设，即I组mGluRs的下调有助于对重复AMPH给药的行为敏感化。使用多学科方法，将在三种AIM中在啮齿动物体内检验这一假设。在这些AIM中，我们将（1）探索和表征纹状体中mGluR 1和mGluR 5蛋白表达对重复AMPH给药的响应减少，并阐明这种减少的细胞机制，（2）通过检查重复施用AMPH对初免mGluR 1/5的影响，根据mGluR 1/5介导的功能，确定mGluR 1/5表达降低的功能后果。纹状体神经元中介导的细胞和基因组应答，包括磷酸肌醇水解、细胞内Ca 2+释放、MAPK/ERK激活、转录因子（CREB）磷酸化和强啡肽基因表达，和（3）确定下调的mGluR 1/5在行为致敏中的作用，通过检查大鼠对反复给予AMPH的行为致敏作用，其中减少的mGluR 1/5蛋白表达被病毒逆转或恢复。介导的转基因表达或通过蛋白酶体抑制剂，或在通过反义或遗传方法实验性降低mGluR 1/5蛋白的大鼠中。从分子到行为的结果将为药物作用的新分子机制提供证据，并最终有助于通过靶向I组mGluRs开发新的药物疗法，用于治疗由药物滥用引起的各种精神疾病。药物滥用和成瘾是主要的社会、经济和健康问题之一。该应用被提出来发现对滥用药物的成瘾特性至关重要的大脑机制。这项研究计划的结果将促进开发新的药物疗法，以治疗因滥用药物而引起的各种精神疾病。

DESCRIPTION (provided by applicant): Glutamate is a major neurotransmitter in the brain, and its role in drug addiction remains a hot topic in animal research aimed to unravel neurochemical mechanisms for addictive properties of drugs of abuse. This lab has long been supported for studying roles of metabotropic glutamate receptors (mGluRs). In the last period of grant, we have identified that group I mGluRs (mGluR1 and 5 subtypes) that are densely expressed in the striatum are key regulators of drug action. Specifically, activation of group I mGluRs is required for acutely- administered psychostimulant amphetamine (AMPH) to enhance endogenous dynorphin activity in rat striatal neurons, a critical response that was thought to homeostatically inhibit drug effects. One form of long-lasting behavioral plasticity, behavioral sensitization to repeated AMPH injections in rats, is a widely-used animal model because it mimics the intensification of drug craving in human addicts. Interestingly, we have recently found that repeated AMPH administration markedly reduced group I mGluR mRNAs and proteins in the striatum. This raises an innovative question as to whether repeated AMPH injections could progressively downregulate the group I mGluR expression and thus function in activating inhibitory dynorphin and thereby induce behavioral sensitization. In this continuation proposal, a series of experiments was therefore proposed to evaluate an overarching hypothesis that the downregulation of group I mGluRs contributes to behavioral sensitization to repeated AMPH administration. Using multidisciplinary approaches, this hypothesis will be tested in rodents in vivo in three AIMs. In these AIMs, we will (1) explore and characterize the reduction of mGluR1 and mGluR5 protein expression in the striatum in response to repeated AMPH administration, and elucidate cellular mechanisms for such reduction, (2) define functional consequences of reduced mGluR1/5 expression in terms of mGluR1/5-mediated functions by examining effects of repeated AMPH administration on the prime mGluR1/5-mediated cellular and genomic responses in striatal neurons, including phosphoinositide hydrolysis, intracellular Ca2+ release, MAPK/ERK activation, transcription factor (CREB) phosphorylation, and dynorphin gene expression, and (3) define functional roles of the downregulated mGluR1/5 in behavioral sensitization by examining behavioral sensitization to repeated AMPH administration in rats in which reduced mGluR1/5 protein expression is reversed or restored by viral-mediated transgene expression or by proteasome inhibitors, or in rats in which mGluR1/5 proteins are experimentally reduced by an antisense or genetic approach. Results achieved here from molecule to behavior will provide evidence for a new molecular mechanism underlying drug action, and will ultimately contribute to the development of novel pharmacotherapies, by targeting the group I mGluRs, for the treatment of various mental illnesses stemmed from substance abuse. PUBLIC HEALTH RELEVANCE: Substance abuse and addiction is among major social, economic, and health problems. This application is proposed to discover brain mechanisms critical for the addictive properties of drugs of abuse. The findings through this research project will promote the development of novel pharmacotherapies for the treatment of various mental illnesses stemmed from substance abuse.