Neurotrophic Mechanisms in Cocaine and Opiate Action

摘要 这一R01拨款集中在神经营养机制涉及刺激剂或阿片类药物诱导的可塑性。 伏隔核(NAC)和其他与奖赏相关的脑区。一个特别的焦点是分子 NAC阐述的这些滥用药物改变树突棘密度和形态的基础 中棘神经元(MSN)。在这项竞争性续订申请中解决了四个关键问题。 首先，几乎所有与可卡因诱导的脊柱生长有关的分子机制都会影响瘦身 只有刺，对长时间后看到的蘑菇刺的延迟生长几乎没有洞察力 戒断可卡因自我给药(SA)并与复发相关。最近的工作由这个支持 格兰特发现RAP1B和微管相关蛋白参与控制蘑菇 NAC MSN上的脊椎，这些新的通路将在雄性和雌性小鼠身上进一步描述 拟开展的研究。其次，关于是否依赖于时间的信息很少。 可卡因SA对D1型和D2型MSN中NAC树突棘的影响。我们已经优化了一个 使这种分析成为可能的方法，使得RAP1B和微管的影响将在细胞类型- 具体的方式。然而，我们知道MSN的异构性要大得多：MSN的子集表示为d1 和D2受体，单细胞RNA测序显示了相当多的异质性。在建议的 研究中，我们将通过使用单细胞来表征可卡因对NAC MSN的影响，从而接受这种复杂性 技术我们还将确定在可卡因SA的生命周期中激活的MSN的一小部分 通过使用Arc-CreER2小鼠，这使得能够标记响应于一个刺激(例如，第一次)而激活的细胞 可卡因暴露)，并跟踪这些细胞在药物SA期间随时间的反应。树突棘的特征 对MSN的这些不同子集进行监管是一个高度优先的问题。第三，几个前脑区域发出兴奋性信号 NAC MSN的输入，这对成瘾相关行为的不同方面有贡献，但要少得多 已知这些传入区域内的细胞异质性，以及神经元的不同亚群如何 都受到滥用药物的影响。最近的发现揭示了腹侧海马(VHIP)的不同亚群 锥体神经元表达D1或D2多巴胺受体，提示细胞水平平行 为NAC制定的组织。我们已经证实了这些发现，并进一步发现这样的d1与d2 支配NAC的VHIP神经元对可卡因复吸行为产生相反的影响。这笔赠款 提供了一个完美的场所，在那里提供这些成瘾的细胞类型的初步特征。第四，多 阿片类药物对NAC脊柱可塑性的影响知之甚少，这是我们提出的一个主要知识缺口 以完成拟议研究的整个过程。总之，这项工作将有助于改善 了解与成瘾相关的行为异常的分子、细胞和电路基础，以及 在识别适合未来药物发现工作的靶基因方面提供新的途径。

SUMMARY This R01 grant focuses on neurotrophic mechanisms involved in stimulant- or opioid-induced plasticity in the nucleus accumbens (NAc) and other reward-related brain regions. A particular focus has been the molecular basis by which these drugs of abuse alter the density and morphology of dendritic spines elaborated by NAc medium spiny neurons (MSNs). Four key questions are addressed in this competitive renewal application. First, virtually all molecular mechanisms implicated in mediating cocaine-induced spine growth affect thin spines only, with little insight available into the delayed growth of mushroom spines seen after prolonged withdrawal from cocaine self-administration (SA) and associated with relapse. Recent work supported by this grant has uncovered the involvement of RAP1B and microtubule-associated proteins in controlling mushroom spines on NAc MSNs, and these novel pathways will be further delineated in male and female mice in the proposed research. Second, there is very little information available concerning whether the time-dependent effects of cocaine SA on NAc dendritic spines occur in D1-type or D2-type MSNs. We have optimized a method to enable this analysis such that the effects RAP1B and microtubules will be studied in a cell type- specific manner. However, we know that MSNs are far more heterogeneous: a subset of MSNs express D1 and D2 receptors, and single cell RNA sequencing reveals considerably more heterogeneity. In the proposed studies, we will embrace this complexity by characterizing cocaine’s effects on NAc MSNs by use of single cell technology. We will also identify the small subset of MSNs that are activated during the life cycle of cocaine SA by use of Arc-CreER2 mice, which make it possible to tag cells activated in response to one stimulus (e.g., first cocaine exposure) and track how those cells respond over time during drug SA. Characterizing dendritic spine regulation in these distinct subsets of MSNs is a high priority. Third, several forebrain regions send excitatory inputs to NAc MSNs, which contribute to distinct aspects of addiction-related behaviors, but much less is known about the cellular heterogeneity within those afferent regions, and how the distinct subsets of neurons are affected by drugs of abuse. Recent findings revealed distinct subsets of ventral hippocampal (vHIP) pyramidal neurons that express either D1 or D2 dopamine receptors, suggesting a parallel level of cellular organization as elaborated for NAc. We have confirmed these findings and found further that such D1 vs. D2 vHIP neurons, both of which innervate the NAc, exert opposite effects on cocaine relapse behavior. This grant offers the perfect venue in which to provide initial characterization of these cell types in addiction. Fourth, much less is known about the effects of opioids on NAc spine plasticity, a major gap in knowledge which we propose to fill through the course of the proposed studies. Together, this work will contribute to an improved understanding of the molecular, cellular, and circuit basis of addiction-related behavioral abnormalities, and provide new pathways forward in identifying target genes suitable for future drug discovery efforts.