Exploring the Potential of Glia for Regulating Clinically Relevant Opiod Actions

描述（由申请人提供）：最近发现，神经胶质在反复暴露于吗啡时变得逐渐更加活化，并且这种神经胶质活化反过来调节吗啡的作用。这一发现最初是在研究吗啡在脊髓中的疼痛抑制作用时发现的。胶质细胞在决定阿片类药物（如吗啡）的作用方面可能具有根本性的重要性，这种可能性是新颖的，其意义也是重要的。正因为如此，我们建议探索胶质细胞是否也会深刻地改变大脑中重复吗啡的作用。我们相信，胶质细胞将被证明是强大的参与几种现象，目前认为纯粹是由于阿片类药物对神经元的影响而产生的;即依赖/撤回，奖励和厌恶。如果这是真的，它将提供证据表明，胶质细胞不仅在调节阿片类药物的疼痛抑制作用方面发挥着重要作用，而且在与人类阿片类药物滥用和成瘾相关的关键现象中也发挥着重要作用。在考虑了阿片类药物依赖/戒断、奖赏和厌恶的临床重要性以及有关神经胶质参与其中的知识的缺乏之后，我们选择首先确定神经胶质和神经胶质产物发挥重要作用的阿片类药物相关现象的范围，然后再详细分析任何单一现象。我们之所以选择这一策略，是因为它是这一阶段调查的正确方法。获得的数据将为以后详细研究这些现象提供指导，包括吗啡以外的其他阿片类和非阿片类药物的一般性问题。本研究的目的是：（1）明确胶质细胞活化是否参与吗啡依赖的形成和/或维持。这将通过表征在建立阿片样物质依赖之前或之后抑制胶质细胞活化是否影响吗啡戒断的表达来实现。还将评估神经胶质是否导致与依赖诱导阿片类药物给药相关的CNS副作用。(2)表征体内吗啡依赖/戒断引起的胶质细胞变化。在这里，（a）涉及重复吗啡作用的脑区和（B）快速分离的小胶质细胞将分别使用免疫组织化学、蛋白质和/或mRNA分析进行检查。(3)确定胶质细胞激活是否有助于吗啡奖赏或厌恶。这将通过表征胶质细胞激活的抑制是否破坏条件性位置偏好和/或条件性位置厌恶来实现。在这些研究中，将以两种方式实现对胶质细胞活化的抑制：（a）使用2种血脑屏障渗透性胶质细胞活化抑制剂;（B）阻断最近发现的胶质细胞上的非经典阿片受体。 最近发现，神经胶质细胞在反复接触吗啡后变得越来越活跃，这种神经胶质细胞的激活反过来又降低了吗啡抑制疼痛的能力。这一提议扩展了对阿片类药物作用的神经胶质调节的探索，通过研究神经胶质是否有力地参与了目前认为纯粹是阿片类药物对神经元作用的结果而产生的几种现象，即依赖/戒断，奖励和厌恶。如果这被证明是真的，它将提供证据表明，胶质细胞不仅在调节阿片类药物的疼痛抑制作用方面发挥着重要作用，而且在与人类阿片类药物滥用和成瘾相关的关键现象中也发挥着重要作用。

DESCRIPTION (provided by applicant): It has recently been discovered that glia become progressively more activated upon repeated exposure to morphine, & that this glial activation, in turn, modulates morphine's effects. This discovery was originally made in the context of studying the pain suppressive effects of morphine in spinal cord. The possibility that glia may be fundamentally important in determining the effects of opioids such as morphine is novel & important in its implications. Because of this, we propose to explore whether glia may profoundly alter the effects of repeated morphine in brain, as well. We believe that glia will prove to be powerfully involved in several phenomena currently thought to arise purely as a result of opioid effects on neurons; that is, dependence/withdrawal, reward & aversion. If this were true, it would provide evidence that glia are critically involved, not only in modulating the pain-suppressive effects of opioids, but also in key phenomena associated with human opioid abuse & addiction. Having considered the clinical importance of opioid dependence/withdrawal, reward & aversion & the paucity of knowledge regarding glial involvement in any of these, we have chosen to first determine the range of opioid-related phenomena in which glia & glial products play an important role, before detailed analyses of any single phenomenon. We chose this strategy as it is the right approach for this stage of investigation. The data to be obtained will provide guidance as to which of these phenomena should later be studied in detail, including issues of generality to other opioid & non-opioid drugs beyond morphine. The aims of the proposal are: (1) To define whether glial activation contributes to the development &/or maintenance of morphine dependence. This will be accomplished by characterizing whether inhibition of glial activation before or after establishment of opioid dependence impacts the expression of morphine withdrawal. Whether glia contribute to CNS side effects associated with dependence-inducing opioid administration will be assessed as well. (2) To characterize changes induced in glia by in vivo morphine dependence/withdrawal. Here, (a) brain regions implicated in the effects of repeated morphine & (b) rapidly isolated microglia will each be examined using immunohistochemical, protein &/or mRNA analyses. (3) To define whether glial activation contributes to morphine reward or aversion. This will be accomplished by characterizing whether inhibition of glial activation disrupts conditioned place preference &/or conditioned place aversion. In these studies, inhibition of glial activation will be accomplished in 2 ways: (a) using 2 blood-brain barrier permeable glial activation inhibitors & (b) blocking the recently discovered non-classical opioid receptor on glia. It has recently been discovered that glia become progressively more activated upon repeated exposure to morphine & that this glial activation, in turn, decreases the ability of morphine to suppress pain. This proposal extends the exploration of glial regulation of opioid actions, by examining whether glia are powerfully involved in several phenomena currently thought to arise purely as a result of opioid effects on neurons; that is, dependence/withdrawal, reward & aversion. If this proves true, it would provide evidence that glia are critically involved, not only in modulating the pain-suppressive effects of opioids, but also in key phenomena associated with human opioid abuse & addiction.