The role of Aberrant Morphological Striatal Plasticity in Dyskinesia Development

描述(由申请人提供)： 纹状体中棘神经元(MSN)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部位，这是正常运动行为所必需的。在晚期帕金森病(PD)中，MSN上的树突和棘突明显萎缩(例如：McNeill等人，1988)。在患有严重DA耗竭的小鼠和大鼠中也观察到了类似的病理(例如：Day等人，2006年)。重要的是，已发现一种新的机制，涉及脊髓内Cav1.3 L型钙离子通道的失调，解释了纹状体DA耗竭后脊柱丢失的原因。给大鼠服用钙通道拮抗剂尼莫地平，或者在转基因小鼠中缺乏这些通道，可以防止脊椎丢失，尽管DA严重枯竭(Day等人，2006年)。帕金森病纹状体中MSN树突形态的改变对LIDs的疗效和/或发展的影响尚不清楚。然而，可以预见的是，在帕金森病纹状体中缺乏这些关键的输入部位将使标准的左旋多巴治疗在突触连接改变时难以概括正常的生理反应，并可能导致异常的可塑性，从而导致左旋多巴诱导的运动障碍(LDS)的发生。建议的研究旨在验证这样一种假设，即纹状体MSN上树突棘的丢失是与LIDs的发育密切相关的关键步骤，防止脊椎丢失将消除或减少LIDs的发育。这些研究的设计还将允许测试另外两个新的假设：1)慢性左旋多巴后纹状体发生异常突触重构，是导致LIDs发展的关键特征；2)MSN脊椎密度降低在严重帕金森病患者经典的基底节运动缺陷和抗帕金森药物反应性降低中起关键作用。为了验证提出的假说，我们将通过比较一系列特定的行为测试来检验脊柱丢失在异常运动障碍和/或广泛性运动障碍发展中的作用，这些大鼠接受以下两种治疗：1)尼莫地平预防脊柱丢失，2)允许典型树突状脊柱丢失的对照组。对高尔基体染色的纹状体MSN进行定量和定性的显微分析，并将其与特定行为相关联。此外，还将对高度富含树突棘的突触支架蛋白SPINOPHILIN/Neurabin 2的蛋白质进行蛋白质印迹分析，以帮助我们了解这种结构蛋白的变化如何伴随着树突棘结构的形态变化。对于许多帕金森患者来说，运动障碍是治疗的一种虚弱和昂贵的副作用：这些异常运动的原因尚不清楚。这一建议旨在通过研究异常神经元通讯在其发育中的作用来加强我们对运动障碍潜在的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.