Progressive dopamine loss:effect of exercise on striatal and nigral glutamate

描述（由申请人提供）： 1-甲基-4-苯基-1，2，3，6-四氢吡啶（1-methyl-4-phenyl-1，2，3，6-tetrahydropyridine，MPTP）是一种全身性神经毒素，常用于引起从黑质丘脑部（substantia nigra pars rectata，SNpc）到尾状核/壳核（caudate/putamen，CPu）的多巴胺（dopamine，DA）输入的部分损失。这也改变了对CPu和黑质（SN）的谷氨酸输入。MPTP后，CPu的基础细胞外谷氨酸水平降低，SN增加。注射谷氨酸受体激动剂到CPu导致帕金森病，这表明谷氨酸突触内至少CPu发挥了重要作用的发展与PD相关的运动问题。 CPu内DA和谷氨酸之间的不平衡在与PD相关的运动问题中起着关键作用，并且在急性MPTP处理的小鼠中在跑步机运动后部分逆转。在最后一次亚急性MPTP给药后1天开始的强制跑步机运动导致SN和CPu中DA神经元和标记物的部分恢复，并改善步态/体力活动。然而，由于SNpc中DA神经元的非进行性50%损失，这种亚急性模型是有限的。我们已经开发了一种新的渐进模型增加DA损失和运动功能障碍，通过每周增加剂量的MPTP超过4周。MPTP 4周后SNpc中DA神经元减少62%，与PD患者中报告的相似。 在进行性MPTP治疗后，CPu中神经末梢谷氨酸免疫金标记的密度增加，表明谷氨酸的积累和释放减少。 我们还发现MPTP诱导的CPu内几种谷氨酸转运蛋白标志物的变化（01 - 02 VGLUT 1/2、EAAC 1、GLAST、GLT-1），这将分别与细胞外谷氨酸的减少或增加一致，如通过体内微透析测量的。此外，跑步机 在幼稚小鼠中的运动导致CPu细胞外谷氨酸的减少。 本项目的总体目标是确定跑步机和自愿跑步轮运动的影响，干预）或随后（即，恢复）渐进给药MPTP对年轻和老年小鼠中CPu/SNpc内谷氨酸和运动功能的改变的影响。该建议的总体假设是MPTP对CPu谷氨酸的影响在运动后将增强，但在SN中的运动将逆转，导致运动功能的恢复和CPu/SNpc中DA标记物的部分恢复。这些变化在谷氨酸和DA标记物，运动功能将发生在更大程度上以下跑步机与转轮运动，并在年轻相比，老年小鼠。本提案的具体目标是：（1）！确定强制跑步机相对于自愿跑步轮运动的效果，在开始进行MPTP给药后2周开始（即，干预），持续MPTP 2周以上，运动4周，对CPu/SN中的谷氨酸和DA标记物，以及年轻和老年小鼠的运动功能，2.）确定在开始进行性MPTP给药后4周开始的强制跑步机相对于自愿转轮运动的效果（即，恢复），持续运动4周，对CPu/SN中的谷氨酸和DA标记物，以及年轻和老年小鼠的运动功能，以及3.）确定跑步机运动期间CPu谷氨酸水平的增加是否会阻止MPTP后SNpc中DA神经元和运动功能的运动诱导恢复。为了模拟跑步机运动的效果，在MPTP治疗期间将在SN中阻断谷氨酸受体。

DESCRIPTION (provided by applicant): 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a systemic neurotoxin commonly used to produce partial loss of at least the dopamine (DA) input from the substantia nigra pars compacta (SNpc) to the caudate/putamen (CPu). This also alters the glutamate input to the CPu and substantia nigra (SN). Following MPTP, there is a decrease in the basal extracellular glutamate levels in the CPu and an increase in the SN. Injection of a glutamate receptor agonist into the CPu leads to parkinsonism, suggesting that glutamate synapses within at least the CPu play an important role in the development of the movement problems associated with PD. The imbalance between DA and glutamate within the CPu plays a critical role in the movement problems associated with PD and is partially reversed following treadmill exercise in acute MPTP treated mice. Forced treadmill exercise, starting 1 day after the last dose of subacute MPTP, resulted in partial recovery of DA neurons and markers in the SN and CPu, and improved gait/physical activity. However, this subacute model is limited due to a non-progressive 50% loss of DA neurons in the SNpc. We have developed a new progressive model of increased DA loss and motor dysfunction via weekly increased dosing of MPTP over 4 weeks. The 62% decrease in DA neurons in the SNpc after 4 weeks of MPTP is similar to that reported in patients with PD. There is an increase in the density of nerve terminal glutamate immuno-gold labeling in the CPu following progressive MPTP treatment, suggesting a buildup of glutamate and a decrease in release. We also find MPTP-induced changes in several glutamate transporter markers within the CPu (VGLUT 1, EAAC1, GLAST) and SN ( VGLUT 1/2, EAAC1, GLAST, GLT-1) that would be consistent with the decrease or increase in extracellular glutamate, respectively, as measured by in vivo microdialysis. In addition, treadmill exercise in naive mice results in a decrease in CPu extracellular glutamate. The overall goal of this project is to determine the effects of treadmill and voluntary running wheel exercise initiated during (i.e., intervention) or following (i.e., restoration) progressive dosing of MPTP on alterations in glutamate within the CPu/SNpc and motor function in both young and aged mice. The overarching hypothesis of this proposal is that the effects of MPTP on CPu glutamate will be augmented following exercise, but will be reversed by exercise in the SN, leading to recovery of motor function and partial restoration of DA markers in the CPu/SNpc. These changes in glutamate and DA markers, and motor function will occur to a greater extent following treadmill versus running wheel exercise and in younger compared to older mice. The specific aims of this proposal are to 1.)!determine the effect of forced treadmill versus voluntary running wheel exercise, beginning 2 weeks after the start of progressive MPTP administration (i.e., intervention) with continued MPTP for 2 more weeks and exercise for 4 weeks, on glutamate and DA markers in the CPu/SN, and motor function in both young and aged mice, 2.) determine the effect of forced treadmill versus voluntary running wheel exercise beginning 4 weeks after the start of progressive MPTP administration (i.e., restoration) with continued exercise for 4 weeks, on glutamate and DA markers in the CPu/SN, and motor function in both young and aged mice, and 3.) determine if increasing CPu glutamate levels during treadmill exercise will block the exercise-induced recovery of DA neurons in the SNpc and motor function following MPTP. To mimic the effect of treadmill exercise, glutamate receptors will be blocked in the SN during MPTP treatment.