Adenosine, Glutamate and Neurodegeneration

描述(申请人提供)：帕金森病(PD)是一种衰弱的疾病，由多巴胺能黑质纹状体神经元的进行性丧失引起。这种神经退化的潜在原因尚不清楚。我们目前的研究集中在了解腺苷和谷氨酸在介导DAR能神经变性中的关系，特别是在代谢应激条件下，如线粒体缺陷的PD患者可能发生的情况。在初步研究中，在纹状体施加代谢应激(通过注入丙二酸盐来阻断电子传递链的复合体II)提高了黑质(SN)的细胞外谷氨酸水平。此外，阻断黑质中的谷氨酸N-甲基-D-天冬氨酸(NMDA)或腺苷A2a受体，而不是纹状体中的腺苷A2a受体，可保护DA能神经元免受线粒体应激的影响。基于这些发现，我们假设纹状体代谢应激导致黑质谷氨酸释放，A2a拮抗剂或代谢型谷氨酸2/3激动剂通过抑制黑质突触前谷氨酸释放来保护应激诱导的神经元变性。这一假说将在大鼠纹状体内注射线粒体抑制剂和注射谷氨酸或腺苷能作用剂的情况下进行验证。将通过纹状体的神经化学指标(酪氨酸羟基酶、多巴胺和代谢物的含量)和黑质的免疫组织化学方法(TH和TH-/Nissl神经元的体视学细胞计数(AIMS#2、3、4)来检验这些干预措施是否能够保护DAR能神经元免受纹状体代谢应激的影响。将使用微透析技术评估这些干预措施改变SN中谷氨酸释放的能力(目标#1、2、3)。在其他研究中，将损害丘脑底核，以确定从该脑区到SN的投射是否是谷氨酸升高的来源，以及A2a受体是否位于这些STN-黑质投射上(AIMS#4，5)。

DESCRIPTION (provided by applicant): Parkinson's disease (PD) is a debilitating disorder that results from the progressive loss of dopaminergic (DAergic) nigrostriatal neurons. Underlying causes of this neurodegeneration are not known. Our current studies focus on understanding the relationship between adenosine and glutamate in mediating DAergic neurodegeneration, particularly under conditions of a metabolic stress as may occur in PD patients with defective mitochondria. In preliminary studies, the imposition of a metabolic stress in the striatum (via an infusion of malonate which blocks complex II of the electron transport chain) elevated extracellular glutamate levels in the substantia nigra (SN). Furthermore, blockade of glutamate N-methyl-D-aspartate (NMDA) or adenosine A2a receptors in the SN, but not the striatum, protected DAergic neurons against the mitochondrial stress. Based on these findings, we hypothesize that a striatal metabolic stress causes glutamate release in the SN and that A2a antagonists or metabotrobic glutamate group 2/3 agonists protect against stress-induced neuronal degeneration by inhibiting presynaptic glutamate release in the substantial nigra. This hypothesis will be tested in rats using intrastriatal infusion of a mitochondrial inhibitor in conjunction with the administration of either glutamatergic- or adenosinergic-acting agents. The ability of these interventions to protect DAergic neurons against a striatal metabolic stress will be examined by neurochemical measures in the striatum (content of tyrosine hydroxylase, dopamine and metabolites) and immunohistochemistry in the substantia nigra (stereological cell counts of TH+ and TH-/Nissl+ neurons (Aims #2,3,4). The ability of these interventions to modify glutamate release in the SN will be assessed using microdialysis techniques (Aims #1,2,3). In other studies, the subthalamic nucleus will be lesioned to determine if projections from this brain region to the SN are the source of the elevated glutamate and if A2a receptors are located on these STN-nigral projections (Aims #4,5).