DOPAMINE AND HYPOXIC/ISCHEMIC INSULT IN NEWBORN BRAIN

这项研究将探讨多巴胺的机制， 缺氧/缺血引起的代谢应激和功能障碍 新生小猪的大脑。它将集中在纹状体，一个丰富的区域， 由黑质纹状体多巴胺能通路支配， 特别容易受到缺血性损伤。代谢压力将是 通过代谢稳态的紊乱来评估;表达增强 HSP-72基因，诱导细胞凋亡，改变毛喉素结合（a 腺苷酸环化酶活性的测量）和多巴胺受体改变 约束力我们的实验模型将利用缺氧/缺血条件 从那些引起可测量但完全可逆的细胞应激 到导致显著神经元死亡和坏死的那些。水平和 将仔细控制缺氧/缺血损伤的持续时间， 通过使用测量纹状体和皮质中的氧分压来定量 磷光的氧依赖性猝灭。 待检验的假设为： 1.多巴胺在体内大脑中的代谢是非常敏感的， 皮层毛细血管床中氧气压力的变化。 2.在新生仔猪的纹状体中，多巴胺有助于发育 细胞代谢和细胞功能的缺血/缺氧紊乱 通过： a. NMDA受体的过度刺激。 B.在化合物的自发自氧化过程中自由基的产生 在缺血/缺氧期间和其酶促释放期间释放过量多巴胺 通过单胺氧化酶氧化。 c.引起D1样和D2样蛋白敏感性的改变 通过改变激动剂的Kd和/或受体的数量 （Bmax）。 3.热休克蛋白-72基因的表达及诱导 细胞凋亡，在纹状体缺氧/缺血条件下， 再氧化，部分由多巴胺介导。 4.严重缺血/缺氧发作时多巴胺过度释放 至少部分负责神经元损伤的发展， 新生仔猪的纹状体。 神经元细胞死亡是脑损伤最常用的终点， 在我们的研究中只测量最严重的条件，因为我们的 主要重点是了解影响代谢的因素， 干扰，而它们仍然是可逆的。作为一种机制， 多巴胺对代谢紊乱的影响是定量的， 可以设计出阻止有害物质并增强免疫力的治疗方法 有益效果，最大限度地减少神经元干扰和 神经元死亡

This study will investigate the mechanisms by which dopamine contributes to metabolic stress and dysfunction induced by hypoxia/ischemia in the brain of newborn piglets. It will focus on the striatum, a region richly innervated by the nigrostriatal dopaminergic pathway and which is particularly susceptible to ischemic injury. Metabolic stress will be evaluated by the disturbance of metabolic homeostasis; enhanced expression of the HSP-72 gene, induction of apoptosis, altered forskolin binding (a measure of activated adenylate cyclase), and altered dopamine receptor binding. Our experimental models will utilize hypoxic/ischemic conditions ranging from those causing measurable but fully reversible cellular stress to those leading to significant neuronal death and necrosis. The level and duration of the hypoxic/ischemic insult will be carefully controlled and quantitated by measuring oxygen pressure in the striatum and cortex using oxygen dependent quenching of phosphorescence. Hypotheses to be tested are: 1. Metabolism of dopamine in the brain in vivo is very sensitive to changes in oxygen pressure in the capillary bed of the cortex. 2. In the striatum of newborn piglets, dopamine contributes to development of ischemic/hypoxic disturbance of cellular metabolism and cell function through: a.Overstimulation of the NMDA receptors. b.Generation of free radicals during spontaneous autooxidation of the excess dopamine released during ischemia/hypoxia and during its enzymatic oxidation by monoamine oxidase. c.Causing alterations in the sensitivity of the D1-like and D2-like receptors by modifying the Kd for agonists and/or the number of receptors (Bmax). 3. Expression of the heat shock protein-72 gene and induction of apoptosis, in striatum during hypoxic/ischemic conditions and reoxygenation, is partially mediated by dopamine. 4. Excessive release of dopamine during severe ischemic/hypoxic episodes is at least partly responsible for development of neuronal injury in striatum of newborn piglets. Neuronal cell death, the most often used end point for brain injury, will be measured in our study only for the most severe conditions, since our primary focus is on understanding the factors influencing the metabolic disturbances while they are still reversible. As the mechanism(s) by which dopamine influences the metabolic disturbance are quantitated, it will be possible to devise treatments which block the detrimental and enhance the beneficial effects, minimizing neuronal disturbance and the possibility of neuronal death.