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Desensitization and Internalization of Mu-Opioid Receptors in the Locus Coeruleus

蓝斑 Mu-阿片受体的脱敏和内化

基本信息

批准号：
7501240
负责人：
Nidia Quillinan
金额：
$ 4.1万
依托单位：
OREGON HEALTH & SCIENCE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2007
资助国家：
美国
起止时间：
2007-09-30 至 2009-09-29
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Opioids are widely used analgesics; however prolonged use results in tolerance, a progressively decreasing responsiveness to the drug. Desensitization and internalization of u-opioid receptors (MOR) are important in the actions of opioids and appear to contribute to the development of tolerance. Desensitization and internalization have been well characterized in naive cells, but how these processes are regulated in neurons during chronic treatment is unclear. Knowing what cellular adaptations occur in response to chronic agonist exposure will better our understanding of the mechanisms contributing to tolerance. The purpose of this proposal is to investigate how regulation of u-opioid receptor desensitization and endocytosis are altered during chronic morphine treatment. Acute desensitization is an uncoupling of the receptor from G-protein activation that occurs during a sustained application of a high concentration of agonist. Agonist-bound receptors also undergo endocytosis. I hypothesize that an upregulation of agonist-induced internalization occurs in chronic-morphine treated animals, resulting in reduced recovery from desensitization. This hypothesis is based on studies examining alterations in the actions of opioids in rat locus coeruleus neurons following chronic-morphine treatment. Agonist efficacy was decreased, desensitization was facilitated, and recovery was incomplete in LC neurons from chronic-morphine-treated rats. To test my hypothesis, I will record MOR coupling to activation of potassium channels in locus coeruleus (LC) neurons from mice expressing a FLAG-tagged u-opioid receptor (FLAG-MOR). This will allow us to study MOR coupling and trafficking simultaneously in a live brain slice. The first goal of this project is to characterize activation, desensitization, and internalization of FLAG-MOR to [Met]5-enkephalin in naTve cells using a combination of electrophysiology and imaging. The second goal is to treat mice chronically with morphine and determine what role internalization plays in the reduced recovery from desensitization that is observed. Understanding the cellular mechanisms of MOR regulation during chronic exposure to morphine will provide insight into the processes that lead to the development of tolerance to opioids. This understanding may allow for the development of effective analgesics which do not produce tolerance.

描述（由申请人提供）：阿片类药物是广泛使用的镇痛剂;然而，长期使用会导致耐受性，对药物的反应性逐渐降低。μ-阿片受体（莫尔）的脱敏和内化在阿片类药物的作用中是重要的，并且似乎有助于耐受性的发展。脱敏和内化已经在幼稚细胞中得到了很好的表征，但是在慢性治疗期间这些过程在神经元中是如何调节的尚不清楚。了解慢性激动剂暴露后发生的细胞适应性变化将有助于我们更好地理解耐受性的机制。本研究的目的是探讨慢性吗啡治疗过程中，阿片受体脱敏和内吞的调节如何改变。急性脱敏是在持续应用高浓度激动剂期间发生的受体与G蛋白活化的解偶联。激动剂结合的受体也经历内吞作用。我推测，激动剂诱导的内化发生在慢性吗啡治疗的动物，导致减少恢复脱敏。这一假设是基于研究慢性吗啡治疗后大鼠蓝斑神经元中阿片类药物作用的改变。激动剂的效力下降，脱敏促进，恢复是不完全的LC神经元从慢性吗啡治疗的大鼠。为了验证我的假设，我将记录莫尔偶联到来自表达FLAG标记的u-阿片受体（FLAG-莫尔）的小鼠的蓝斑（LC）神经元中钾通道的激活。这将使我们能够在活体脑切片中同时研究莫尔偶联和运输。该项目的第一个目标是使用电生理学和成像的组合来表征天然细胞中FLAG-MOR对[Met]5-脑啡肽的激活、脱敏和内化。第二个目标是用吗啡长期治疗小鼠，并确定内化在观察到的脱敏恢复减少中起什么作用。了解慢性吗啡暴露过程中莫尔调节的细胞机制将有助于深入了解阿片类药物耐受性发展的过程。这种理解可能允许开发不产生耐受性的有效镇痛剂。