Chronic methamphetamine-induced catecholaminergic degeneration and cognitive dysfunction

项目摘要/摘要 甲基苯丙胺(冰毒)是一种强烈上瘾的精神刺激剂，能够导致神经元损伤。 我的导师格雷夫斯博士最近的研究发现，冰毒增加了脑神经轴突中的线粒体应激 黑质致密部(SNC)多巴胺(DA)神经元源于胞质DA的MAO代谢。 初步研究表明，蓝斑(LC)去甲肾上腺素(NE)神经元的轴突也有类似的影响。vbl.使用 一种28天的冰毒给药范例，Graves博士最近的研究发现SNC DA神经元变性 MAO的药理抑制具有神经保护作用。初步研究同样显示慢性冰毒- 诱导LC变性，MAO抑制可减轻这种变性。这些数据表明轴突MAO- 依赖的线粒体应激导致慢性冰毒诱导的变性。的首要目标是 这一建议是为了确定变性的进展和表现，无论是神经元(相对于 对于星形细胞)MAO酶是退化所必需的，而慢性的行为后果 冰毒诱导的SNC和LC变性。我的中心假设是慢性冰毒能诱导神经细胞 MAO依赖的SNC和LC变性死亡模式导致认知功能障碍和 将在以下目标中进行测试：目标1：确定慢性冰毒是否会导致SNC的死亡模式 和LC退变。冰毒增加轴突，但不增加躯体MAO依赖的线粒体应激，MAO 抑制预防冰毒诱导的慢性SNC和LC退变；这些数据表明MAO依赖 轴突线粒体应激导致退行性变。因此我假设慢性冰毒会产生一种 SNC和LC变性的消退模式，轴突丢失先于躯体丢失。目标2：确定 慢性冰毒所致的SNC和LC变性是否需要神经元MAO。研究表明系统性 MAO抑制可防止冰毒诱导的慢性SNC和LC变性，但MAO酶表达 在神经元和星形胶质细胞中。鉴于冰毒增加了SNC和LC轴突的线粒体应激，我假设 神经元MAO是退化所必需的。目标3：确定慢性病的行为后果 冰毒诱导的SNC和LC变性。SNC退变和LC损伤与损伤相关 分别在新颖的物体识别和上下文相关的恐惧条件分析中；因此 假设慢性冰毒诱导的SNC和LC退变将导致类似的行为 减损。我将通过训练和使用免疫荧光、无偏见的体视学来检验我的假设 神经元和轴突退行性变的评估、行为分析以及遗传学和药理学 MAO酶的抑制。测试我的假设将为我提供出色的技术和概念 作为一名研究科学家接受培训。完成拟议的目标将提高我们对 慢性冰毒的神经退行性后果，扩大对儿茶酚胺能变性的认识 对类似退行性疾病的研究具有一定的参考价值。

PROJECT SUMMARY/ABSTRACT Methamphetamine (meth) is a powerfully addictive psychostimulant capable of causing neuronal damage. Recent studies by my mentor, Dr. Graves, found that meth increases mitochondrial stress in the axons of substantia nigra pars compacta (SNc) dopamine (DA) neurons resulting from MAO metabolism of cytosolic DA. Pilot studies showed similar effects in the axons of Locus coeruleus (LC) norepinephrine (NE) neurons. Using a 28-day meth administration paradigm, recent studies by Dr. Graves found degeneration of SNc DA neurons and that pharmacological inhibition of MAO was neuroprotective. Pilot studies similarly show chronic meth- induced LC degeneration that is attenuated by MAO inhibition. These data suggest that axonal MAO- dependent mitochondrial stress contributes to chronic meth-induced degeneration. The overarching goal of this proposal is to determine the progression and presentation of degeneration, whether neuronal (as opposed to astrocytic) MAO enzymes are necessary for degeneration, and the behavioral consequences of chronic meth-induced SNc and LC degeneration. My central hypothesis is that chronic meth induces a neuronal MAO-dependent dying-back pattern of SNc and LC degeneration resulting in cognitive impairment and will be tested in the following aims: Aim 1: Determine if chronic meth produces a dying-back pattern of SNc and LC degeneration. Meth increases axonal, but not somatic MAO-dependent mitochondrial stress, and MAO inhibition prevented chronic meth-induced SNc and LC degeneration; these data suggest that MAO-dependent axonal mitochondrial stress drives degeneration. I therefore hypothesize that chronic meth will produce a dying-back pattern of SNc and LC degeneration, where axonal loss precedes somatic loss. Aim 2: Determine if neuronal MAO is necessary for chronic meth-induced SNc and LC degeneration. Studies show systemic MAO inhibition prevented chronic meth-induced SNc and LC degeneration, but MAO enzymes are expressed in neurons and astrocytes. Given that meth increased mitochondrial stress in SNc and LC axons, I hypothesize that neuronal MAO is necessary for degeneration. Aim 3: Determine the behavioral consequences of chronic meth-induced SNc and LC degeneration. SNc degeneration and LC lesioning are associated with impairments in novel object recognition and context-associated fear conditioning assays, respectively; I therefore hypothesize that chronic meth-induced degeneration of the SNc and LC will lead to similar behavioral impairments. I will test my hypotheses by training in and using immunofluorescence, unbiased stereological assessment of neuronal and axonal degeneration, behavioral analysis, and both genetic and pharmacological inhibition of MAO enzymes. Testing my hypotheses will provide me with outstanding technical and conceptual training as a research scientist. Completion of proposed aims will improve our understanding of the neurodegenerative consequences of chronic meth, expanding knowledge of catecholaminergic degeneration and providing value to the study of disorders involving similar degeneration.