SIGMA RECEPTOR SIGNALING IN FOCAL CEREBRAL ISCHEMIA

兴奋性氨基酸是缺血性脑损伤的组成部分 机制等由于σ受体配体调节神经元对 体外药理学N-甲基-D-天冬氨酸（NMDA）受体刺激 通过特定的σ配体识别位点，它们具有潜在的 治疗价值，可能与中风无关 一系列限制临床应用的不良副作用 NMDA受体拮抗剂 4-苯基-1-（4-苯基丁基）哌啶（PPBP）是一种典型的σ- 受体配体，提供神经保护，但确切的机制， 以前在体内没有引起保护作用。结论来自 体外实验表明，σ受体配体可能会干扰 与兴奋性氨基酸诱导的神经毒性相互作用， NMDA受体复合物。此外，σ-受体配体可以有利地 减少兴奋性毒性神经递质和儿茶酚胺释放， 局部缺血尤其是谷氨酸和多巴胺这个项目的总体目标是 项目是定义体内信号传导过程， σ-受体配体在短暂性脑缺血中的显著神经保护特性 局部缺血一般的假设是，这些配体保护 通过独特的σ受体途径抑制兴奋毒素 释放和NMDA激活，并因此防止随后的神经元 一氧化氮合酶（nNOS）活化和细胞死亡。具体目标 将：定义最有效的治疗模式sigma-受体 配体，PPBP，在短暂的局灶性缺血;确定是否σ-受体 激活抑制局灶性缺血性脑损伤的兴奋毒性机制; 表征基础和缺血后σ受体信号传导机制 体内;确定σ受体介导的 神经保护特异于NOS的组成型神经元同种型。 该方法将包括使用血管内螺纹闭塞 啮齿类动物（大鼠和小鼠）的短暂局灶性缺血模型， 微透析测量自发和NMDA刺激的NOS活性， 微透析法测定兴奋性氨基酸和多巴胺 代谢物，免疫化学检测G蛋白， 放射自显影用于测量σ受体分布。这些 技术相结合，以测试的假设，σ受体配体 通过以下方式改善神经学结局（组织学和神经功能）： 在缺血期间干扰兴奋性氨基酸机制， 再灌注通过G蛋白第二信使，所有这一切最终 导致NO产生减少和脑损伤减少。

Excitatory amino acids are an integral part of ischemic brain injury mechanisms. Because sigma-receptor ligands modulate neuronal responses to pharmacologic N-methyl D-aspartate (NMDA) receptor stimulation in vitro via a specific sigma ligand recognition site, they are of potential therapeutic value in stroke and may not be associate with the same spectrum of undesired side-effects which limit the clinical utility of NMDA receptor antagonists 4-phenyl-1-(4-phenylbutyl) piperidine (PPBP) is a prototypic sigma- receptor ligand which provides neuroprotection but the exact mechanism of protection has not been previously elicited in vivo. Conclusions from in vitro experiments have suggested that sigma-receptor ligands may interfere with excitatory amino acid-induced neurotoxicity by interacting with the NMDA receptor complex. Further, sigma-receptor ligands may advantageously decrease excitotoxic neurotransmitter and catecholamine release during ischemia, specifically glutamate and dopamine. The overall goal of this project is to define the in vivo signaling process that accounts for the marked neuroprotective properties of sigma-receptor ligands in transient focal ischemia. The general hypothesis is that these ligands protect the brain by a unique sigma-receptor pathway which inhibits excitotoxin release and NMDA activation, and, therefore, prevents consequent neuronal nitric oxide synthase (nNOS) activation and cell death. The specific aims will: define the most efficacious treatment paradigm sigma-receptor ligand, PPBP, in transient focal ischemia; determine if sigma-receptor activation inhibits excitotoxic mechanisms of focal ischemic brain injury; characterize basal and post-ischemic sigma-receptor signaling mechanisms in vivo; determine if sigma receptor mediated mechanisms of neuroprotection are specific to the constitutive neuronal isoform of NOS. The methodology will include use of an intravascular thread occlusion model of transient focal ischemia in rodents (both rats and mice), microdialysis measurement of spontaneous and NMDA-stimulated NOS activity, microdialysis measurement of excitatory amino acids and dopamine with its metabolites, immunochemistry for detection of G-protein and autoradiography for measurement of sigma-receptor distribution. These techniques are combined to test the hypothesis that sigma-receptor ligands improve neurologic outcome (histology and neurologic function) by interfering with excitatory amino acid mechanisms during ischemia and reperfusion through a G-protein second messenger, all which ultimately result in decreased production of NO and decreased brain injury.