GABA channels and dopamine in striatum

描述(申请人提供)：纹状体控制学习的运动行为的执行，以及抑制不想要的动作。纹状体的主要神经元类型为中棘神经元(MSN)，从皮质和丘脑接受谷氨酸能汇聚神经支配，从黑质接受多巴胺能神经支配。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，从而顺利控制运动输出。这种控制是通过GABAA受体的时相激活和紧张性激活来实现的。本项目旨在比较起源于纹状体苍白质和纹状体黑质通路的MSN中GABA受体介导的电流和受体亚型。我们将利用从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GABAA受体的独特性质。我们将使用皮质纹状体脑片中的单细胞电生理学来检验这一假设，即部分纹状体GABAA受体具有独特的性质，并且在纹状体投射神经元的两个主要亚型之间分布不均。根据初步数据显示纹状体蛋白表达由GABAA通道亚型介导的紧张性电导，第一个特定目的是努力了解GABAA受体的α和β亚基在MSN中产生这种紧张性激活的作用。这将通过亚基选择性药物、缺乏特定亚基的小鼠和与纹状体MSN相关的重组GABA通道来完成。第二个目标将测试蛋白激酶磷酸化调节张力活跃的GABA通道的功能特性的假设。最后一个目的将调查MSN亚型中特定和独特的多巴胺受体的存在是否在设定GABA受体亚型的特性和调节GABA受体亚型的表达方面发挥作用，这些亚型可以作为纹状体功能障碍相关疾病的药物治疗靶点。 公共卫生相关性：纹状体和纹状体中的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。以前的报告表明，多巴胺耗竭会导致GABA受体的变化，从而加剧这种纹状体输出的不平衡。此外，全身应用GABAA受体激动剂Muscimol，可增加多巴胺受体D2基因敲除小鼠的运动活性，同时减少野生型小鼠的运动。使用标记了两个主要纹状体输出通路的转基因小鼠，我们将有一个独特的机会来回答一个基本问题：紧张性和相性GABA电导在纹状体疾病中扮演什么角色？由于GABAA受体具有相当成熟的药理作用，这项拟议的研究很有可能确定治疗与纹状体功能障碍相关的疾病的新靶点，包括帕金森氏病、亨廷顿病、迟发性运动障碍、多发性抽动症和药物成瘾。此外，由于两类主要的DA受体的药理学在精神疾病中具有如此关键的作用，我们将获得的结果，尽管明显与基础神经科学有关，但将在神经疾病和精神健康方面都有显著的应用。

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.