The role of Aberrant Morphological Striatal Plasticity in Dyskinesia Development

描述（由申请人提供）： 在纹状体的中型多刺神经元（MSNs）上发现的许多树突棘是多巴胺（DA）和谷氨酸输入的突触整合的关键位点，这对于正常运动行为是必不可少的。在晚期帕金森病（PD）中，MSN上的树突和棘显著萎缩（例如：麦克尼尔等人，1988年）。在严重DA耗竭的小鼠和大鼠中观察到类似的病理学（例如：Day等人，2006）。重要的是，一个新的机制，涉及intraspine Cav1.3 L-型Ca 2+通道的失调已被发现，占脊髓损失后纹状体DA耗竭。对大鼠施用钙通道拮抗剂尼莫地平，或在转基因小鼠中不存在这些通道，尽管严重的DA消耗，仍能防止脊柱丢失（Day等人，2006年）。帕金森病纹状体中MSN的树突形态改变对LID的疗效和/或发展的影响尚不清楚。然而，可以预期的是，帕金森病纹状体中这些关键输入位点的缺失将使得标准左旋多巴疗法在面对改变的突触连接时难以重现正常的生理反应，并且可能导致异常可塑性，从而导致左旋多巴诱导的运动障碍（LID）的发展。拟议的研究旨在验证以下假设：纹状体MSN上树突棘的丢失是与LID发展密切相关的关键步骤，预防棘丢失将消除或减少LID的发展。这些研究的设计还将允许测试两个额外的新假设：1）纹状体中的异常突触重塑发生在慢性左旋多巴之后，并且是LID发展的关键特征;和2）MSN棘密度的降低在严重帕金森病受试者中的经典基底节运动缺陷和抗帕金森病药物反应性降低中起关键作用。为了检验所提出的假设，我们将通过比较严重DA耗竭大鼠的一系列特定行为测试来检查脊柱丢失在异常运动障碍运动和/或全身运动缺陷发展中的作用：1）尼莫地平预防脊柱丢失，或2）允许典型树突棘丢失的对照载体。将检查高尔基体染色的纹状体MSN的定量和定性显微镜分析，并与特定行为相关。此外，蛋白质spinophilin/neurabin 2，突触支架蛋白高度富集在树突棘蛋白质的蛋白质的蛋白质印迹分析将被检查，以帮助我们了解这些结构蛋白的变化如何伴随树突棘结构的形态学改变。运动障碍是许多帕金森病患者治疗的一种使人衰弱和昂贵的副作用：这些异常运动的原因仍然未知。这项建议旨在通过研究异常神经元通讯在运动障碍发展中的作用，增强我们对运动障碍背后复杂细胞过程的理解。

DESCRIPTION (provided by applicant): The many dendritic spines found on medium spiny neurons (MSNs) in the striatum are critical sites for synaptic integration of dopamine (DA) and glutamate input, which is essential for normal motor behavior. In advanced Parkinson's disease (PD) there is marked atrophy of dendrites and spines on MSNs (eg: McNeill et al., 1988). Similar pathology is observed in mice and rats with severe DA depletion (e.g.: Day et al, 2006). Importantly, a new mechanism involving dysregulation of intraspine Cav1.3 L-type Ca2+ channels has been found to account for spine loss following striatal DA depletion. Administration of the calcium channel antagonist nimodipine to rats, or the absence of these channels in transgenic mice prevents spine loss despite severe DA depletion (Day et al., 2006). The impact of altered dendritic morphology of MSNs in the parkinsonian striatum on efficacy and/or development of LIDs remains unclear. However, it would be anticipated that an absence of these critical input sites in the parkinsonian striatum would make it difficult for standard levodopa therapy to recapitulate normal physiological responses in the face of altered synaptic connectivity, and may lead to aberrant plasticity that results in development of levodopa-induced dyskinesias (LIDs). The proposed studies are aimed at testing the hypothesis that loss of dendritic spines on striatal MSNs is a key step intimately linked to the development of LIDs, and preventing spine loss will eliminate, or reduce development of LIDs. The design of these studies will also allow testing of two additional novel hypotheses: 1) aberrant synaptic remodeling in the striatum occurs following chronic levodopa and is a key feature underlying the development of LIDs; and 2) that reduction of MSN spine density plays a key role in classical basal ganglia motor deficits and decreased anti-parkinsonian drug responsiveness in severely parkinsonian subjects. To test the proposed hypotheses, we will examine the role that spine loss plays in development of abnormal dyskinetic movements and/or generalized motor deficits by comparing a battery of specific behavioral tests in severely DA depleted rats treated either with: 1) nimodipine to prevent spine loss, or 2) control vehicle which allows for typical dendritic spine loss. Quantitative and qualitative microscopic analyses of Golgi stained striatal MSNs will be examined and correlated with specific behaviors. Additionally, western blot analysis of the protein spinophilin/neurabin 2, a synaptic scaffolding protein highly enriched in dendritic spines will be examined to aid our understanding how changes in such structural proteins accompany morphological alterations in dendritic spine structure. Dyskinesias are a debilitating and costly side effect of therapy for many Parkinson's patients: The causes of these abnormal movements remain unknown. This proposal is designed to enhance our understanding of the intricate cellular processes underlying dyskinesias by studying the role of abnormal neuronal communication in their development.