Circuit-Selective Astroglial Plasticity During Opioid Relapse

摘要 吸毒成瘾的一个主要特点是，尽管长期戒断，但仍容易复发。几十年的 研究已经扩大了我们对复发的神经基础的理解，但几乎没有有效的 治疗，恢复自上而下的控制积极和前用户的药物寻求。在动物模型中， 重复使用药物，但不重复暴露于自然奖励，导致体内过量的谷氨酸传输。 在存在奖励相关线索和背景的情况下， 寻找这种行为范式已被用于模拟触发复发的神经适应， 对药物相关线索的反应与人类的药物渴望有关。谷氨酸传递失调 慢性海洛因使用后，部分原因是外周星形胶质细胞过程的持久变化， 活跃的突触并表达谷氨酸转运蛋白GLT-1，这与越来越多的文献一致， 这种细胞类型在维持兴奋性突触传递的完整性方面具有突出的作用。本人已发表 数据显示，NAcore中的星形胶质细胞在对药物的反应中经历了深刻的瞬时形态可塑性， 而不是蔗糖条件的线索，这种可塑性有助于减弱寻求行为。海洛因相关 提示还刺激星形胶质细胞膜上GLT-1的表面接近性增加，这是一种适应， 预期限制临床前模型复发期间的谷氨酸溢出。这项提案的目的是探讨 我所发现的星形胶质细胞可塑性的测量方法是否与皮层神经元的递质释放有关， 在NAcore内的预测，并揭示细胞内信号事件，触发形态可塑性， 星形胶质细胞在寻找药物的过程中。这项提议的最终目标是确定线索诱导的星形胶质细胞 适应影响不同的突触后靶点，因为NAcore中的两种主要神经元亚型，D1- 和D2-MSN差异影响药物寻求行为。在目标1中，我将联合收割机与 体内纤维光度测定法，以确定2小时恢复期间星形胶质细胞可塑性的时程 上网时段在目标2中，我将把光遗传学与共聚焦显微镜配对，以确定谷氨酸是否来自 前边缘皮质终末是驱动星形胶质细胞运动和GLT-1表面扩散所必需的 海洛因的自我管理。在目标3中，我将干扰驱动星形胶质细胞过程的信号级联 在星形胶质细胞中选择性地使用病毒介导的shRNA递送的寻找过程中的运动性。最后，在目标4中，我将 在转基因D1-和D2-Cre大鼠中使用共聚焦显微镜来确定星形胶质细胞过程或表面- 近端GLT-1在线索恢复寻找期间选择性地与D1-或D2-MSN相关联。这些目标将 为我提供光遗传学的全面培训，以及病毒工具，使我能够有选择地 操纵星形胶质细胞中的蛋白质表达，并将我以前的发现与潜在的神经回路联系起来。 这项工作的相关性超出了阿片类药物的复发，并可能对正常的突触 动机行为背后的生理学

Abstract Vulnerability to relapse despite prolonged abstinence is a principal feature of drug addiction. Decades of research have expanded our understanding of the neural basis of relapse, but have yielded few effective treatments that restore top-down control over drug seeking in active and former users. In animal models, repeated drug use, but not repeated exposure to natural rewards, results in excess glutamate transmission within corticofugal projections to the striatum in the presence of reward-associated cues and contexts that drive seeking. This behavioral paradigm has been used to model neural adaptations that trigger relapse, since reactivity to drug-related cues is linked to drug craving in humans. The dysregulation of glutamate transmission after chronic heroin use arises in part from enduring changes in peripheral astrocyte processes that insulate active synapses and express the glutamate transporter GLT-1, consistent with a growing literature that illustrates a prominent role for this cell type in maintaining the integrity of excitatory synaptic transmission. My published data show that astrocytes in the NAcore undergo profound transient morphological plasticity in response to drug- but not sucrose-conditioned cues and that this plasticity serves to attenuate seeking behavior. Heroin-associated cues also stimulate an increase in surface-proximity of GLT-1 on the astroglial membrane, an adaptation expected to limit glutamate spillover during relapse in preclinical models. The goal of this proposal is to explore whether measures of astroglial plasticity that I have discovered are linked to transmitter release from cortical projections within the NAcore and to uncover intracellular signaling events that trigger morphological plasticity in astrocytes during drug-seeking. A final goal of this proposal is to determine whether cue-induced astrocyte adaptations impact different post-synaptic targets, since the two principle neuronal subtypes in the NAcore, D1- and D2-MSNs differentially impact drug seeking behavior. In Aim 1, I will combine confocal microscopy with in vivo fiber photometry in order to identify the time course of astroglial plasticity during a 2-hr reinstatement session. In Aim 2, I will pair optogenetics with confocal microscopy to determine whether glutamate from prelimbic cortical terminals is necessary to drive astrocyte motility and GLT-1 surface diffusion after extinction from heroin self-administration. In Aim 3, I will interfere with the signaling cascade that drives astrocyte process motility during seeking using viral-mediated delivery of shRNAs selectively in astrocytes. Finally, in Aim 4 I will use confocal microscopy in transgenic D1- and D2-Cre rats to determine whether astrocyte processes or surface- proximal GLT-1 are selectively associated with D1- or D2-MSNs during cue-reinstated seeking. These Aims will provide me with comprehensive training in optogenetics as well as with viral tools that will allow me to selectively manipulate protein expression in astrocytes and will link my previous findings with the underlying neural circuitry. The relevance of this work extends beyond relapse to opioids and may have implications for normal synaptic physiology underlying motivated behavior.