NITRIC OXIDE IN FOCAL CEREBRAL ISCHEMIA

有大量的资料表明脑缺血是伴随着 细胞外兴奋性氨基酸的增加。 证据 最近积累的这些兴奋性氨基酸的增加 与神经组织中一氧化氮的产生有关。 体外数据 强烈表明一氧化氮在大脑中的重要作用， 虽然在体内获得的数据有限，但局部缺血， 模棱两可 该项目的主要目的是解决 通过仔细研究， 各种参数。 在猫的局灶性缺血模型中， 在缺血和缺血后组织中的产生将通过 各种技术，包括直接测量一氧化氮， 微电极，一氧化氮合酶活性测定，一氧化氮 氧化合酶免疫组织化学染色（用于神经元，内皮细胞， 巨噬细胞NOS）和NADPH黄递酶染色。 脑血流将 使用激光多普勒进行连续测量， 区域和放射性标记的微球，用于多个区域中的离散测量。 地区。 为了进一步研究一氧化氮可能 脑缺血的功能，微血管通透性的测量 也将作出。 局部缺血将产生暂时闭塞 在猫的左侧大脑中动脉，测量将是 在缺血的急性和慢性阶段进行。 利用 抑制一氧化氮合成的化合物，或 增加组织一氧化氮水平，我们将确定 神经元组织损伤可以通过改变一氧化氮的产生来改变。 该项目的主要假设是， 大脑组织产生一种平衡的对立力量，有些作用， 减少脑缺血（即，血管舒张，由于 一氧化氮对血管平滑肌的作用），以及一些作用于增加 脑缺血性损伤（即，组织中一氧化氮的毒性作用）。 通过适当改变一氧化氮合酶的活性， 减弱缺血时组织一氧化氮的增加， 对血液流动产生不利影响，我们将能够减少 脑缺血后神经元损伤。 使用的药物 优先作用于神经元和内皮组织型一氧化氮 合成酶，并在酶的诱导形式，我们将获得 关于神经元、内皮细胞和 诱导型一氧化氮合成 只有多管齐下， 在同一动物模型中测量多个参数，我们将 能够找出一氧化氮在大脑中的真正作用， 缺血 随着对脑损伤机制的深入了解， 缺血性损伤，治疗方案可以更直接地设计。 如果 作用于一氧化氮/精氨酸系统的化合物被证明是 神经保护，它将提供另一种潜在的治疗途径， 脑缺血

There is significant data indicating the cerebral ischemia is accompanied by an increase in extracellular excitatory amino acids. Evidence has recently accumulated linking the increase in these excitatory amino acids with the production of nitric oxide in neuronal tissue. The in vitro data strongly suggests a significant role for nitric oxide int he cerebral ischemia, while the limited data that has been obtained in vivo, is equivocal. The principal aim of this project is to resolve the apparent discrepancies int he literature by performing careful studies looking at a variety of parameters. In a focal ischemia model in the cat, nitric oxide production in ischemic and postischemic tissue will be monitored by a variety of techniques including the direct measurement of nitric oxide with a microelectrode, measurement of nitric oxide synthase activity, nitric oxide synthase immunohistochemical staining (for neuronal, endothelial, and macrophage NOS), and NADPH diaphorase staining. Cerebral blood flow will be measured using both laser doppler for continuous measurements in one region, and radiolabeled microspheres for discrete measurements in a number of regions. To further investigate the mechanism by which nitric oxide may function in cerebral ischemia, measurements of microvascular permeability will also be made. Focal ischemia will be produced by temporary occlusion of the left middle cerebral artery int he cat, and measurements will be undertaken in both the acute and the chronic stage of ischemia. Utilizing compounds that inhibit the synthesis of nitric oxide, or compounds that increase tissue nitric oxide levels, we will determine if the extent of neuronal tissue damage can be altered by altering nitric oxide production. The primary hypothesis of this project is that local nitric oxide in cerebral tissue produces a balance of opposing forces, some acting to reduce damage in cerebral ischemia (ie. vasodilation, due to the action of nitric oxide ont he vascular smooth muscle), and some acting to augment cerebral ischemic damage (ie. toxic action of nitric oxide in the tissue). By appropriately modifying the activity of nitric oxide synthase so as to attenuate the tissue nitric oxide increases that occur in ischemia without adversely affecting blood flow, we will be able to reduce the extent of neuronal damage following cerebral ischemia. Using drugs which act preferentially on the neuronal and endothelial constitutive nitric oxide synthase, and on the inducible form of the enzyme, we will obtain information on the relateive importance of neuronal, endothelial, and inducible nitric oxide synthesis. Only by using a multi-prong approach, where a number of parameters are measured int he same animal model, will we be able to sort out the true role that nitric oxide plays in cerebral ischemia. With a better understanding of the mechanisms of cerebral ischemic injury, treatment protocols can more directly be designed. If compounds that act on the nitric oxide/arginine system are shown to be neuroprotective, it will provide another potential avenue for the treatment of cerebral ischemia.