Cholinesterase Inhibitors, Axonal Transport, and Memory

项目概要 由于有机磷农药的广泛使用，其对人类健康构成了持续的威胁 以及他们在恐怖袭击中的潜在用途对有机磷农药的急性毒性进行了广泛的研究; 然而，长期或反复暴露于不产生明显症状的OP水平的后果 对急性毒性的了解很少。此外，有临床证据表明，这种低水平的暴露， OP导致认知功能的长期缺陷，尽管这种影响的机制尚不清楚。一个长- 我们实验室的长期目标是阐明负责延长神经行为的机制， 与慢性低水平OP暴露相关的缺陷，因此更有效的治疗策略可以 发展。我们在最初资助期间进行的实验结果表明，低- 水平暴露于商业农药毒死蜱，导致前脉冲抑制的长期缺陷 （前注意处理的模型）和空间学习，而不显着影响运动功能。 此外，毒死蜱与神经营养素受体和胆碱能蛋白的减少有关， 对认知功能很重要的大脑区域。这些赤字伴随着 在离体坐骨神经中测量的轴突运输。然而，缺乏的分子机制， 轴突运输和这种对轴突运输的影响在脑中发生的程度尚不清楚。的 本申请的目的是鉴定负责轴突运输改变的机制， 并进一步确定低水平OP暴露对认知功能的长期影响。我们的中央 假设是OP共价修饰参与轴突运输的关键蛋白， 修饰损害了支持认知功能的神经元通路的功能。实现我们 目标，我们提出了三个具体目标：1）确定慢性低水平暴露的后果， 关于注意力和认知灵活性的代表性OP，2）确定慢性低水平 暴露于代表性OP对脑中轴突运输的影响，以及3）确定分子机制 负责OP诱导的轴突运输缺陷。为了实现这些目标，我们将使用五个选择 连续反应时间任务，以评估持续的注意力，水迷宫任务，以衡量灭绝（一种形式的 认知灵活性）和立体定位注射可追踪的葡聚糖、免疫组织化学和质量 光谱法测定OP对脑中轴突运输的影响及其后果 损伤该项目的意义及其与公共卫生的相关性在于， 根据OP对动物信息处理基本组成部分的长期影响来定义OP， 我们将解决一个根本的差距，我们的知识如何OP可能影响人类随着时间的推移。的 实验将有助于更好地了解与一类化学品有关的毒性， 继续对全世界数百万人构成重大环境风险。

¿ PROJECT SUMMARY Organophosphates (OPs) pose a constant threat to human health due to their widespread use as pesticides and their potential employment in terrorist attacks. The acute toxicity of OPs has been extensively studied; however, the consequences of prolonged or repeated exposure to levels of OPs that produce no overt signs of acute toxicity are poorly understood. Further, there is clinical evidence that such low-level exposures to OPs leads to prolonged deficits in cognition, although the mechanism for this effect is unknown. One long- term goal of our laboratories is to elucidate the mechanisms responsible for the prolonged neurobehavioral deficits associated with chronic low-level OP exposures such that more effective therapeutic strategies can be developed. The results of our experiments conducted during the initial funding period established that low- level exposures to the commercial pesticide, chlorpyrifos, resulted in protracted deficits in prepulse inhibition (a model of pre-attentive processing) and spatial learning without significantly affecting locomotor function. Further, chlorpyrifos was associated with decreases in neurotrophin receptors and cholinergic proteins in brain regions that are important to cognitive function. These deficits were accompanied by decreases in axonal transport measured in sciatic nerves ex vivo. However, the molecular mechanisms for the deficits in axonal transport and the extent to which such effects on axonal transport occur in the brain are unclear. The objective of this application is to identify the mechanisms responsible for alterations in axonal transport as well as to further define the long-term effects of low-level OP exposure on cognitive function. Our central hypothesis is that OPs covalently modify key proteins that are involved in axonal transport and that such modifications compromise the function of neuronal pathways that support cognitive function. To achieve our objective, we propose three specific aims: 1) Determine the consequences of chronic low-level exposure to representative OPs on attention and cognitive flexibility, 2) Determine the consequences of chronic low-level exposure to representative OPs on axonal transport in the brain, and 3) Identify the molecular mechanisms responsible for OP-induced deficits in axonal transport. To address these aims, we will use a five choice serial reaction time task to assess sustained attention, a water maze task to measure extinction (a form of cognitive flexibility) and stereotaxic injections of traceable dextrans, immunohistochemistry, and mass spectrometry to determine OP effects on axonal transport in the brain and the consequences of its impairment. The significance of this project and its relevance to public health is that by mechanistically defining OPs based on their long-term effects on essential components of information processing in animals, we will have addressed a fundamental gap in our knowledge of how OPs likely affect humans over time. The experiments will contribute to a better understanding of the toxicity associated with a class of chemicals that continues to pose a significant environmental risk to millions of people worldwide.