METABOTROPIC GLUTAMATE RECEPTORS AND EXCITOTOXICITY

描述(申请人提供)：谷氨酸是大脑中最普遍的神经递质。代谢性谷氨酸受体(MGluRs)是一类G蛋白偶联受体，调节大脑兴奋性突触的神经传递。MGluR亚型的多样性和异质性分布可能为开发药物提供机会，以选择性地针对特定的中枢神经系统，并改善不同神经疾病的症状。然而，mGluRs在兴奋性毒性中的作用仍然存在争议。外侧隔核是边缘系统的主要中继核。在外侧隔神经元，mGluR激动剂可诱发癫痫样放电，并显著增加细胞内游离钙离子浓度。初步数据表明，钙离子的增加会导致严重的兴奋性毒性，这种毒性不依赖于离子型谷氨酸受体。本研究的目的是确定大鼠外侧隔区mGluRs的分子性质，它介导癫痫发作、放电和兴奋毒性。在AIML，将测试新一代基团选择性激动剂和拮抗剂。细胞内记录将被用来研究这些药物对外侧隔神经元放电模式的影响。切片的兴奋毒性将通过碘化丙啶(PI)负载量和荧光玉染色进行评估。这些实验将确定癫痫样放电和兴奋性毒性是否仅由I组mGluRs介导。在目标2中，将产生靶向大鼠mGluRl或mGluRs的siRNA试剂，并用于功能沉默大鼠隔器官型培养中mGluR1或mGluRs的表达。然后将评估选择性降低mGluR1或mGluRs表达对mGluR介导的兴奋性毒性的影响。通过结合药理学和RNA干扰的方法，mGluRs介导癫痫发作和外侧隔神经元兴奋毒性的分子本质将被阐明。这一发现将为开发可用于治疗帕金森氏症、癫痫、精神病和与中风相关的兴奋性毒性的药物提供关键信息。

DESCRIPTION (provided by applicant): Glutamate is the most prevalent neurotransmitter in the brain. Metabotropic glutamate receptors (mGluRs) are a family of G-protein coupled receptors that regulate neurotransmission at excitatory synapses in the brain. The diversity and heterogeneous distribution of mGluR subtypes may provide an opportunity for developing drugs to selectively target a specific CNS system and ameliorate symptoms of distinct neurological disorders. However, the role of mGluRs in excitotoxicity remains controversial. The lateral septal nucleus is a major relay nucleus in the limbic system. In lateral septal neurons, mGluR agonists elicit epileptiform burst firing and greatly elevate intracellular free calcium. Preliminary data suggest that this calcium increase results in severe excitotoxicity that is independent of ionotropic glutamate receptors. The goal of this study is to determine the molecular nature of the mGluRs in the lateral septum of rats that mediate the epileptic burst firing and excitotoxicity. In Aiml, a new generation of group selective agonists and antagonists will be tested. Intracellular recordings will be used to study the effects of these drugs on the firing pattern of lateral septal neurons. Excitotoxicity in the slices will be assessed by propidium iodide (PI) loading and fluoro-jade staining. These experiments will determine whether epileptiform burst firing and excitotoxicity are mediated by group I mGluRs alone. In Aim 2, siRNA reagents that target rat mGluRl or mGluRS will be generated and used to functionally silence the expression of mGluRl or mGluRS in organotypic cultures of the rat septum. The effect of selectively reducing mGluRl or mGluRS expression on mGluR-mediated excitotoxicity will then be assessed. By combining pharmacological and RNA-interference approaches, the molecular nature of the mGluRs that mediate the epileptic burst firing and excitotoxicity in lateral septal neurons will be elucidated. The findings will provide critical information for developing drugs that can be used to treat Parkinson's diseases, seizures, psychosis and excitotoxicity associated with stroke.