MU OPIOID RECEPTOR AND TOLERANCE DEVELOPMENT

吗啡和其他阿片类药物广泛用于临床治疗 剧烈的疼痛。长期使用吗啡的一个问题是耐受性 发展起来。吗啡主要作用于Mu阿片受体。 吗啡耐受性的形成是一个复杂的过程，涉及到变化 在细胞水平和神经回路中。尽管进行了大量研究， 吗啡耐受的机制仍不是很清楚，部分原因是 因为没有细胞模型可以使Mu受体 被操纵来解决特定的问题。最近一种Mu阿片受体 已经被分子克隆，从而第一次使其成为可能 来生成这样的细胞模型。这是当前的目标 求婚。 这项调查的基本假设是 在细胞水平上的吗啡耐受性由特定的 通过Mu阿片受体介导的分子事件。二 哺乳动物细胞系、PC12嗜铬细胞瘤细胞和中国仓鼠 卵巢细胞，将被用来稳定表达Mu受体。联结 CAMP通路和离子通道的Mu受体将被确定 接受急性阿片类药物治疗。那么，吗啡耐受性的发展将 通过将细胞长期暴露在吗啡中并确定 耐受性变化背后的分子事件 发展。此外，磷酸化在调节中的作用 受体功能的研究将通过系统地突变 蛋白激酶A和C的潜在磷酸化位点，产生 表达突变受体的细胞系，并检测其影响 这些突变对受体功能的影响。这些细胞也将是 以确定长期接触吗啡的潜在作用 耐受性形成中的受体磷酸化。 这些研究将提供有关分子的重要信息。 通过Mu阿片受体产生耐受的机制。是这样的 信息将有助于我们了解阿片类药物可能的作用 AT受体，并将为设计策略提供基础 避免阿片类药物耐受问题在临床治疗中的应用 疼痛。

Morphine and other opioids are widely used in clinical management of severe pain. One problem of prolonged use of morphine is that tolerance develops. Morphine exerts its effects mainly at the mu opioid receptors. Development of morphine tolerance is a complex process, involving changes at the cellular level and in neural circuitry. Despite numerous studies, mechanisms for morphine tolerance are still not well-understood, partly because there are no cellular models in which the mu receptor can be manipulated to address specific questions. Recently a mu opioid receptor has been molecularly cloned, thus making it possible for the first time to generate such cellular models. This is the goal of the present proposal. The underlying hypothesis for this investigation is that the development of morphine tolerance at the cellular level results from specific molecular events that are mediated through the mu opioid receptor. Two mammalian cell lines, PC12 pheochromocytoma cells and Chinese hamster ovary cells, will be used to stably express the mu receptor. Coupling of the mu receptor to the cAMP pathway and ion channels will be determined with acute opioid treatment. Then, development of morphine tolerance will be studied by chronically exposing the cells to morphine and determining the molecular events that underlie the changes during tolerance development. Furthermore, the role of phosphorylation in regulating receptor function will be studied by systematically mutating the potential phosphorylation sites of protein kinases A and C, generating cell lines that express the mutant receptors, and examining the effect of these mutations on receptor function. These cells will also be chronically exposed to morphine to determine the potential role of receptor phosphorylation in tolerance development. These studies will provide important information as to the molecular mechanisms of tolerance development through the mu opioid receptor. Such information will contribute to our knowledge on how opioid drugs may act at receptors and will provide a basis in designing strategies to circumvent the problem of opioid tolerance in the clinical management of pain.