Exploring the Potential of Glia for Regulating Clinically Relevant Opiod Actions

描述(申请人提供)：最近发现，反复接触吗啡后，神经胶质细胞变得越来越活跃，而这种神经胶质细胞的激活反过来又调节了吗啡的作用。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做出的。神经胶质细胞可能在决定吗啡等阿片类药物的作用中起着根本性的重要作用，这一可能性是新颖的，其重要意义在于它的含义。正因为如此，我们建议探索胶质细胞是否也可以深刻地改变重复使用吗啡对大脑的影响。我们相信，胶质细胞将有力地参与目前被认为纯粹是由于阿片类药物对神经元的影响而产生的几种现象，即依赖/戒断、奖赏和厌恶。如果这是真的，这将提供证据表明，胶质细胞参与了关键的参与，不仅调节阿片类药物的疼痛抑制效应，而且还参与了与人类阿片类药物滥用和成瘾相关的关键现象。考虑到阿片依赖/戒断、奖赏和厌恶的临床重要性以及关于神经胶质参与其中任何一种的知识匮乏，我们选择首先确定与阿片相关的现象的范围，其中胶质细胞和神经胶质产物在其中发挥重要作用，然后再对任何单一现象进行详细分析。我们之所以选择这一策略，是因为它是现阶段调查的正确方法。将获得的数据将指导今后应详细研究这些现象中的哪些现象，包括除吗啡以外的其他阿片和非阿片类药物的一般性问题。该提案的目的是：(1)确定神经胶质细胞的激活是否有助于吗啡依赖的发展和/或维持。这将通过确定在阿片类药物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实现。还将评估神经胶质细胞是否会导致与阿片类药物依赖治疗相关的中枢神经系统副作用。(2)研究吗啡依赖/戒断对神经胶质细胞的影响。在这里，(A)涉及反复吗啡影响的脑区和(B)快速分离的小胶质细胞将分别用免疫组织化学、蛋白质和/或信使核糖核酸分析进行检测。(3)明确神经胶质细胞的激活是否参与了吗啡的奖赏或厌恶。这将通过表征神经胶质激活的抑制是否扰乱条件性位置偏爱和/或条件性位置厌恶来实现。在这些研究中，对胶质细胞激活的抑制将通过两种方式完成：(A)使用两种血脑屏障通透性神经胶质激活抑制剂；(B)阻断最近发现的神经胶质细胞上的非经典阿片受体。最近发现，反复接触吗啡后，神经胶质细胞逐渐变得更加活跃，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。这一建议扩展了神经胶质对阿片类药物作用的调控的探索，通过检查胶质细胞是否强烈地参与了目前被认为纯粹是由于阿片类药物对神经元的影响而产生的几种现象，即依赖/戒断、奖赏和厌恶。如果这被证明是真的，它将提供证据，证明胶质细胞参与了关键的参与，不仅参与了阿片类药物的疼痛抑制效应，而且还参与了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 This discovery was originally made in the context of studying the pain suppressive effects of morphine in spinal cord.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.