Modulation of G protein coupled receptor function

吗啡、可待因和度冷丁等阿片激动剂仍然是治疗慢性疼痛最常用和最有效的治疗方法。尽管慢性阿片类药物治疗会产生高度的耐受性和身体依赖。对阿片类药物在脑内的耐受和依赖机制尚不清楚，但很明显，慢性阿片类药物治疗会在特定的脑区产生显著的受体脱敏。此外，疼痛本身，以及与腺苷和α2-肾上腺素能激动剂等药物的同时治疗，都会改变患者对阿片类药物治疗的敏感性。阿片受体(包括mu型、delta型和kappa型)以及腺苷A1和α2-肾上腺素能受体是G蛋白偶联受体，它们激活信号转导系统的能力可以由激动剂刺激膜和切片放射自显影结合[35S]GTP GammaS的能力来决定。该项目将利用药物治疗、自我给药和其他中枢组件开发的慢性疼痛模型，研究大鼠脊髓中几种受体/G蛋白相互作用的调节。首先，在确定阿片和腺苷A1激动剂激活脊髓G蛋白的急性有效性后，将在脊髓膜和放射自显影中检测慢性药物暴露产生受体脱敏的能力。这些治疗将包括鞘内慢性给药以脱敏阿片受体激活的G蛋白，以及鞘内慢性给药腺苷和可乐定以脱敏激动剂刺激的[32P]AAGTP进入特定G蛋白亚基。其次，我们将在脊神经结扎的大鼠的大脑和脊髓中检测各种受体激活的G蛋白活性，以确定慢性疼痛和超敏反应是否影响受体/G蛋白偶联。这些研究还将确定慢性疼痛状态如何调节脊髓中G蛋白的基础水平和活动。第三，NMDA拮抗剂和蛋白激酶C抑制剂调节受体脱敏的能力将在长期鞘内给药后进行测试。来自该项目的信息将有助于在临床核心中设计研究，以测试不同疗效的阿片激动剂在治疗慢性疼痛中的使用。此外，这些研究将提供信息，以最大限度地减少长期药物治疗慢性疼痛的耐受性。

Opioid agonists like morphine, codeine and meperidine remain the most commonly used and effective treatment for chronic pain conditions. Despite the fact that chronic opioid treatment can produce high levels of tolerance and physical dependence. Mechanisms of tolerance and dependence for in brain are not well understood, but it is clear that chronic opioid treatment produces significant receptor desensitization in specific brain regions. Moreover, pain itself, as well as concurrent treatment with drugs like adenosine and alpha2- adrenergic agonists, alter the sensitivity of patients to opioid treatment. Opioid receptors (including mu, delta and kappa types), as well as adenosine A1 and alpha2-adrenergic receptors, are G-protein-coupled receptors, and their ability to activate signal transduction systems can be determined by the ability of agonists to stimulate [35S]GTPgammaS binding in both membranes and section autoradiography. This project will examine regulation of several receptor/G-protein interactions in rat spinal cord, using models of drug treatment, self-administration and chronic pain developed by other Center components. First, after determining the acute efficacies of opioid and adenosine A1 agonists in activating G-proteins in spinal cord, the ability of chronic drug exposure to produce receptor desensitization will be examined in both spinal cord membranes and by autoradiography. These treatments will include chronic intrathecal opioid administration to desensitize opioid receptor-activated G-proteins, and chronic intrathecal administration of adenosine and clonidine to desensitize agonist-stimulated incorporation of [32P]AAGTP into specific G-protein subunits. Second, various receptor-activated G-protein activities will be determined in both brains ans spinal cords from spinal nerve ligated rats to determine whether chronic pain and hypersensitivity affect receptor/G-protein coupling. These studies will also determine how chronic pain states modulate basal levels and activities of G-proteins in spinal cord. Third, the ability of NMDA antagonists and protein kinase C inhibitors to modulate receptor desensitization will be tested after chronic intrathecal administration of drugs. Information from this project will help design studies in the Clinical Core to test the use of opioid agonists of differing efficacies in treating chronic pain. Moreover, these studies will provide information to minimize tolerance in long-term drug treatment of chronic pain.