GABA channels and dopamine in striatum

描述（由申请人提供）：纹状体控制学习的运动行为的执行以及对不想要的运动的抑制。纹状体中的主要神经元类型，即中型多刺神经元（MSN），接受来自皮质和丘脑的会聚性多巴胺能神经支配和来自黑质的多巴胺能神经支配。此外，少量GABA能中间神经元控制大量MSN的兴奋性，以维持信息流出的适当平衡，从而平稳控制运动输出。这种控制通过阶段性和紧张性GABA α受体激活来实现。本项目旨在比较GABA受体介导的电流和受体亚型之间的MSN起源的纹状体和纹状体黑质途径。我们将利用由在D1或D2多巴胺受体表达细胞中选择性表达绿色或红色荧光蛋白的小鼠品系制成的皮质纹状体切片来鉴定这些细胞中GABA α受体的独特性质。皮质纹状体切片中的单细胞电生理学将用于检验以下假设：纹状体GABA a受体的一部分具有独特的性质，并且在纹状体投射神经元的两种主要亚型之间不均匀分布。基于初步数据显示，纹状体的MSN表达由GABA α通道的亚型介导的紧张性传导，第一个具体的目标将努力了解GABA α受体的α和β亚基在MSN中产生这种紧张性激活的作用。这将与亚基选择性药物，小鼠缺乏特定的亚基和重组GABA通道相关的纹状体MSN。第二个目标将测试的假设，蛋白激酶磷酸化调节紧张活性GABA通道的功能特性。最后一个目的将调查MSN亚型中特异性和独特的多巴胺受体的存在是否在设置特性和调节GABA受体亚型的表达中起作用，所述GABA受体亚型可以是与纹状体功能障碍相关的疾病的药理学治疗的靶点。 公共卫生相关性：纹状体苍白球和纹状体黑质中棘神经元是哺乳动物纹状体的主要输出神经元，控制运动并在运动障碍中变得不平衡。先前的报告表明，多巴胺耗竭诱导GABA受体的变化，这加剧了纹状体输出的不平衡。此外，全身施用GABAA受体激动剂蝇蕈醇增加了多巴胺受体D2敲除小鼠（帕金森病模型）的运动活性，同时减少了野生型小鼠的运动。使用两个主要的纹状体输出通路标记的转基因小鼠，我们将有一个独特的机会来回答一个基本的问题：什么样的作用紧张和相位GABA电导纹状体疾病？由于GABA α受体具有相当成熟的药理学，因此所提出的研究具有很大的潜力来确定用于治疗与纹状体功能障碍相关的疾病的新的治疗靶点，所述疾病包括帕金森病、亨廷顿病、迟发性运动障碍、图雷特综合征和药物成瘾。此外，由于两大类DA受体的药理学在精神疾病中具有如此重要的作用，我们将得出的结果尽管与基础神经科学明显相关，但对神经系统疾病和精神健康都有显着的应用。

DESCRIPTION (provided by applicant): The striatum controls the execution of learned motor behaviors as well as the suppression of unwanted movements. The main neuronal type in the striatum, the medium spiny neuron (MSN), receives converging glutamatergic innervation from the cortex and thalamus and dopaminergic innervation from the substantia nigra. In addition a small population of GABAergic interneurons controls the excitability of a vast population of MSNs to maintain the proper balance of information outflow for smooth control of motor output. This control is exerted via both phasic and tonic GABAa receptor activation. This project aims to compare GABA receptor-mediated currents and the receptor subtypes amongst MSNs originating the striatopallidal and the striatonigral pathways. We will utilize corticostriatal slices made from strains of mice which selectively express green or red fluorescent protein in D1 or D2 dopamine receptor expressing cells to identify unique properties of GABAa receptors in these cells. Single cell electrophysiology in corticostriatal slices will be used to test the hypothesis that that a portion of striatal GABAa receptors have unique properties and are unequally distributed between the two major subtypes of striatal projection neurons. Based on preliminary data showing that striatopallidal MSN express a tonic conductance mediated by a subtype of GABAa channel, the first specific aim will strive to understand the role of alpha and beta subunits of GABAa receptors in producing this tonic activation in MSNs. This will be done with subunit selective drugs, mice lacking specific subunits and recombinant GABA channels relevant to striatal MSNs. The second aims will test the hypothesis that protein kinase phosphorylation regulates the functional properties of tonically active GABA channels. The last aim will investigate if the presence of the specific and distinct dopamine receptors in MSN subtypes plays a role in setting the properties and regulating the expression of GABA receptor subtypes that can be target for pharmacological therapy of disorders associated with striatal dysfunction. PUBLIC HEALTH RELEVANCE: Striatopallidal and striatonigral medium spiny neurons are the major output neurons from the mammalian striatum, control movements and become imbalanced in movement disorders. Previous reports have suggested that dopamine depletion induces changes in GABA receptors which exacerbate this imbalance of striatal output. Additionally, the systemic administration of the GABAA receptor agonist muscimol, increased locomotor activity in dopamine receptor D2 knockout mice, a model of Parkinson's disease while reducing locomotion in wild type mice. Using transgenic mice with the two major striatal output pathways labeled, we will have a unique opportunity to answer a fundamental question: What role tonic and phasic GABA conductance plays in striatal disorders? As GABAa receptor have a quite established pharmacology, the proposed study has great potential to identify novel therapeutic targets for treating disorders associated with striatal dysfunction including Parkinson's disease, Huntington's disease, tardive dyskinesia, Tourette's syndrome and drug addiction. In addition, as the pharmacology of two major classes of DA receptors has such critical role in mental illness, the results we will derive, although clearly related to basic neuroscience, will have notable applications to both neurological disorders and to mental health.