Exploring the Potential of Glia for Regulating Clinically Relevant Opiod Actions

描述（由申请人提供）：最近发现，神经胶质细胞在反复暴露于吗啡后逐渐变得更加激活，而这种神经胶质细胞的激活反过来调节吗啡的作用。这一发现最初是在研究吗啡对脊髓疼痛抑制作用的背景下发现的。神经胶质可能在决定阿片类药物（如吗啡）的作用方面具有根本的重要意义，这一可能性是新颖且重要的。正因为如此，我们建议探索神经胶质是否也可能深刻地改变吗啡在大脑中的作用。我们相信，神经胶质将被证明有力地参与了目前被认为纯粹是由于阿片类物质对神经元的影响而产生的几种现象；也就是依赖/退缩，奖励与厌恶。如果这是真的，它将提供证据，证明神经胶质细胞不仅参与调节阿片类药物的疼痛抑制作用，而且还参与与人类阿片类药物滥用和成瘾相关的关键现象。考虑到阿片类药物依赖/戒断，奖励和厌恶的临床重要性以及关于胶质参与其中的知识的缺乏，我们选择首先确定胶质和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。我们选择了这种策略，因为这是现阶段调查的正确方法。”获得的数据将为以后应详细研究哪些现象提供指导，包括对吗啡以外的其他阿片类药物和非阿片类药物的一般性问题。该提案的目的是：(1)确定神经胶质激活是否有助于吗啡依赖的发展和/或维持。这将通过在阿片依赖建立之前或之后抑制胶质细胞激活是否影响吗啡戒断的表达来完成。神经胶质细胞是否参与与阿片类药物依赖诱导相关的中枢神经系统副作用也将被评估。(2)观察吗啡依赖/戒断对神经胶质细胞的影响。在这里，(a)与重复吗啡作用有关的大脑区域和(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)确定神经胶质激活是否有助于吗啡的奖励或厌恶。这将通过表征抑制神经胶质激活是否会破坏条件位置偏好和/或条件位置厌恶来完成。在这些研究中，抑制胶质细胞的激活将通过两种方式完成：(a)使用2种血脑屏障渗透性胶质细胞激活抑制剂和(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，而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。这一建议扩展了对阿片作用的神经胶质调节的探索，通过检查神经胶质是否有力地参与了目前被认为纯粹是由于阿片对神经元的作用而产生的几种现象；也就是依赖/退缩，奖励与厌恶。如果这被证明是正确的，它将提供证据，证明神经胶质细胞不仅参与调节阿片类药物的疼痛抑制作用，而且还参与与人类阿片类药物滥用和成瘾相关的关键现象。

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 This discovery was originally made in the context of studying the pain suppressive effects of morphine in spinal cord.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.