Morphine tolerance in live neurons

活神经元的吗啡耐受性

• 批准号: 8452833
• 负责人: Erica Sawyer Levitt
• 金额: $ 5.22万
• 依托单位: OREGON HEALTH & SCIENCE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-04-01 至 2014-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8452833
• 关键词: ARRB2; Agonist; Animals; Brain; Cells; Chronic; Clinic; Coupled; Development; Dose; Effectiveness; Electrophysiology (science); Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Excision; G protein-coupled inwardly-rectifying potassium channel; GTP-Binding Proteins; Goals; Hour; In Vitro; Injection of therapeutic agent; Knockout Mice; Learning; Life; Ligands; Long-Term Effects; Measures; Mediating; Morphine; Mus; Neurons; Okadaic Acid; Opioid; Pain; Patients; Pharmaceutical Preparations; Phosphoric Monoester Hydrolases; Phosphorylation; Potassium; Property; Protein Dephosphorylation; Rattus; Recovery; Regimen; Risk; Role; Signal Transduction; Slice; Testing; Therapeutic; Time; Tissues; Work; addiction; arrestin 2; chronic pain; clinically relevant; desensitization; locus ceruleus structure; mu opioid receptors; novel therapeutics; phosphatase inhibitor; prevent; receptor; research study; response; voltage clamp

DESCRIPTION (provided by applicant): Morphine is one of the most commonly prescribed opioids to treat pain. However, prolonged use often leads to the development of tolerance characterized by loss of effectiveness and dose escalation. Morphine tolerance is in part due to a loss of signaling from mu opioid receptors (MOR) independent of a change in receptor levels. Despite years of study, the mechanisms causing this loss of signaling remain unsolved. Traditionally, tolerance is measured in cells or tissue removed from a chronically treated animal and washed free of morphine for several hours. Preliminary experiments have discovered that if brain slices from a morphine-treated rat are instead maintained in morphine continuously, the morphine response is significantly smaller compared to slices in which morphine was washed out, indicating that a portion of tolerance can recover within a relatively short wash. This rapid recovery following morphine removal is newly identified and may have appreciable importance to the persistence of tolerance. The goal of this proposal is to better understand morphine tolerance by carefully examining the often overlooked desensitization that is maintained by the continuous presence of morphine. The overall hypothesis is that two types of tolerance (long-lasting tolerance and chronic desensitization) develop during long-term morphine treatment distinguished by the time-course of recovery, which have different mechanisms and depend on treatment paradigm. This hypothesis will be tested using locus coeruleus neurons contained in brain slices from naove or morphine-treated animals. Morphine effects will be measured using whole-cell voltage-clamp electrophysiology to detect MOR-mediated activation of G protein-coupled inwardly rectifying potassium (GIRK) channels. The specific aims of this proposal are as follows: (1) to identify the long-lasting tolerance and chronic desensitization that results from long-term continuous morphine treatment of rats and mice, (2) to compare this to tolerance and desensitization following long-term intermittent morphine treatment and (3) to determine the role of 2-arrestin 2 in the development of long-lasting tolerance (using 2-arrestin 2 knockout mice) and the role of ser/thr phosphatases in development of and recovery from chronic desensitization (using okadaic acid). Together, this proposal will provide new information about chronic desensitization that develops after long-term morphine treatment. Focusing on morphine specifically will help identify mechanisms involved in tolerance to this most commonly used opioid agonist.

描述（由申请人提供）：吗啡是治疗疼痛最常用的处方阿片类药物之一。然而，长期使用往往导致以药效丧失和剂量增加为特征的耐受性的发展。吗啡耐受在一定程度上是由于来自mu阿片受体（MOR）的信号丧失而独立于受体水平的变化。尽管经过多年的研究，导致这种信号丢失的机制仍未得到解决。传统上，耐受性是通过从长期治疗的动物身上取出的细胞或组织来测量的，这些细胞或组织在没有吗啡的情况下洗涤几个小时。初步实验发现，如果将吗啡治疗过的大鼠的大脑切片持续保持在吗啡中，与吗啡被洗掉的大脑切片相比，吗啡的反应要小得多，这表明在相对较短的洗涤时间内，部分耐受性可以恢复。这种快速恢复吗啡移除后是新发现的，可能对耐受性的持久性有明显的重要性。这一建议的目的是通过仔细检查经常被忽视的脱敏作用来更好地理解吗啡耐受性，这种脱敏作用是由吗啡持续存在所维持的。总体假设：长期吗啡治疗过程中出现两种耐受性（持久耐受性和慢性脱敏性），其机制不同，且取决于治疗模式。这一假设将通过使用幼年或吗啡治疗动物的脑切片中含有的蓝斑神经元进行验证。吗啡效应将采用全细胞电压钳电生理学来检测莫尔介导的G蛋白偶联内整流钾（GIRK）通道的激活。这项建议的具体目的如下：(1)确定长期连续吗啡治疗大鼠和小鼠的持久耐受性和慢性脱敏，(2)将其与长期间歇吗啡治疗后的耐受性和脱敏进行比较，(3)确定2-抑制素2在持久耐受性的形成中的作用（使用2-抑制素2敲除小鼠）和丝氨酸/苏氨酸磷酸酶在慢性脱敏的形成和恢复中的作用（使用冈田酸）。总之，这一建议将为长期吗啡治疗后出现的慢性脱敏提供新的信息。特别关注吗啡将有助于确定对这种最常用的阿片类激动剂耐受的机制。