SIGMA RECEPTOR SIGNALING IN FOCAL CEREBRAL ISCHEMIA

兴奋性氨基酸是缺血性脑损伤的重要组成部分 机制。因为西格玛受体配体调节神经元反应 体外药理学 N-甲基 D-天冬氨酸 (NMDA) 受体刺激 通过特定的西格玛配体识别位点，它们具有潜力 中风的治疗价值，可能与中风无关 一系列不良副作用限制了其临床应用 NMDA 受体拮抗剂 4-苯基-1-(4-苯基丁基)哌啶 (PPBP) 是一种原型 sigma- 受体配体提供神经保护，但其确切机制 先前尚未在体内引起保护作用。结论来自于 体外实验表明西格玛受体配体可能会干扰 通过与兴奋性氨基酸相互作用而引起的神经毒性 NMDA 受体复合物。此外，σ受体配体可以有利地 减少兴奋性神经递质和儿茶酚胺的释放 缺血，特别是谷氨酸和多巴胺。本次活动的总体目标 该项目的目的是定义体内信号传导过程 西格玛受体配体在瞬时状态下具有显着的神经保护特性 局灶性缺血。一般假设是这些配体保护 大脑通过独特的西格玛受体途径抑制兴奋毒素 释放和 NMDA 激活，因此可以防止随后的神经元 一氧化氮合酶（nNOS）激活和细胞死亡。具体目标 将：定义最有效的治疗范式西格玛受体 配体，PPBP，在短暂性局灶性缺血中；确定是否是西格玛受体 激活抑制局灶性缺血性脑损伤的兴奋性毒性机制； 表征基础和缺血后 sigma 受体信号传导机制 体内；确定 sigma 受体是否介导的机制 神经保护作用是 NOS 组成型神经元亚型所特有的。 该方法将包括使用血管内线闭塞 啮齿类动物（大鼠和小鼠）短暂性局部缺血模型， 自发和 NMDA 刺激的 NOS 活性的微透析测量， 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 蛋白和 用于测量西格玛受体分布的放射自显影术。这些 结合技术来检验西格玛受体配体的假设 改善神经系统结果（组织学和神经功能） 干扰缺血期间的兴奋性氨基酸机制 通过 G 蛋白第二信使进行再灌注，所有这些最终 导致NO产生减少并减少脑损伤。

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.