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(MPTP)是一种全身性神经毒素，通常用于产生至少部分损失从黑质致密部(SNPC)到尾壳核(CPU)的多巴胺(DA)。这也改变了中央处理器和黑质(SN)的谷氨酸输入。在MPTP后，CPU细胞外基础谷氨酸水平降低，SN升高。将谷氨酸受体激动剂注入中央处理器会导致帕金森综合症，这表明至少中央处理器内的谷氨酸突触在与帕金森病相关的运动问题的发生中发挥了重要作用。 在急性MPTP治疗的小鼠中，CPU内DA和谷氨酸之间的失衡在与帕金森病相关的运动问题中起着关键作用，并在跑步机运动后部分逆转。在末次亚急性MPTP给药后第1天开始强迫跑台运动，可使SN和CPU中DA神经元和标志物部分恢复，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%的丢失，这种亚急性模型是有限的。我们开发了一种新的进展性模型，通过每周增加MPTP的剂量，在4周内增加DA丢失和运动功能障碍。MPTP治疗4周后，SNPC的DA神经元减少62%，与报道的PD患者相似。进行性MPTP治疗后，CPU内神经末梢谷氨酸免疫金标记物密度增加，提示谷氨酸积聚，释放减少。我们还发现MPTP诱导的CPU(VGLUT 1，EAAC1，GLAST)和SN(VGLUT 1/2，EAAC1，GLAST，GLT-1)内的几个谷氨酸转运体标志物的变化，分别与细胞外谷氨酸的减少或增加是一致的，通过活体微透析测量。此外，跑步机 幼稚小鼠的运动导致CPU细胞外谷氨酸的减少。 本项目的总体目标是确定在递增剂量MPTP期间(即干预)或之后(即恢复)开始的跑步机和自愿转轮运动对幼年和老年小鼠CPU/SNPC内谷氨酸和运动功能的变化的影响。本研究的基本假设是，运动后MPTP对CPU谷氨酸的作用增强，而在SN运动则逆转，导致运动功能的恢复和CPU/SNPC中DA标志物的部分恢复。这些谷氨酸和DA标志物以及运动功能的变化将在跑步机运动后发生在更大程度上，而与跑轮运动相比，在更年轻的小鼠中发生的变化也比年长的小鼠更大。这项建议的具体目的是：1.确定强迫跑步机和自愿转轮运动的效果，在开始递进式MPTP给药(即干预)后2周开始，继续MPTP 2周以上，运动4周，对CPU/SN中的谷氨酸和DA标记物以及幼龄和老年小鼠的运动功能的影响，2.)3.确定强制跑步机运动与自愿跑轮运动在MPTP递增给药(即恢复)开始后4周开始，并继续运动4周，对CPU/SN中的谷氨酸和DA标记物以及幼年和老年小鼠的运动功能的影响。确定在跑步机运动中增加CPU谷氨酸水平是否会阻止运动诱导的SNPC中DA神经元的恢复和MPTP后的运动功能。为了模拟跑步机运动的效果，在MPTP治疗期间，SN中的谷氨酸受体将被阻断。

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.