A single-cell atlas of gene expression and chromatin accessibility changes associated with cocaine addiction in the rat amygdala [snRNA-seq]

The amygdala plays a key role in the negative emotional states associated with the relapse to drug seeking behavior. Neuroanatomical and functional observations have uncovered the role of discrete amygdala subregions in different aspects of these negative affective states. However, the underlying transcriptional regulatory programs driving the function of distinct amygdala cell types remains unknown. We generated an atlas of single nucleus gene expression and chromatin accessibility in the amygdala of rats with low and high cocaine addiction-like behaviors after prolonged abstinence from extended access to cocaine intravenous self-administration. We identified thousands of cell type-specific differentially expressed genes, suggesting that negative affective states are associated with cell type-specific mechanisms which are enriched for molecular pathways, including energy metabolism and GABAergic synapses in excitatory and somatostatin neurons. We demonstrate that higher addiction severity is linked to excessive GABAergic inhibition and, using pharmacological inhibition, we find that addiction-like phenotypes are regulated by the metabolite methylglyoxal which is an agonist at GABA-A receptors. By analyzing differences in chromatin accessibility, we predict upstream transcriptional regulators associated with addiction-like behavior and find discordant regulation of key transcription factors among distinct cell populations. Overall, we provide a comprehensive characterization of cell type-specific transcriptional changes in the amygdala during protracted abstinence and use these insights to identify a novel target for pharmacological intervention.杏仁核（amygdala）在与药物觅药行为复吸相关的负性情绪状态中发挥关键调控作用。神经解剖学与功能学观测已揭示，离散的杏仁核亚区在这类负性情感状态的不同维度中承担调控功能。然而，驱动不同杏仁核细胞类型发挥功能的潜在转录调控程序仍未明确。本研究针对表现出不同程度可卡因成瘾样行为（cocaine addiction-like behaviors）、且经延长可卡因静脉自身给药（cocaine intravenous self-administration）操作后经历长期戒断的大鼠，构建了其杏仁核内的单细胞核基因表达（single nucleus gene expression）与染色质可及性（chromatin accessibility）图谱。我们鉴定出数千种细胞类型特异性差异表达基因（differentially expressed genes），提示负性情感状态与细胞类型特异性机制相关，这类机制在兴奋性神经元与生长抑素神经元中富集于能量代谢、γ-氨基丁酸能突触（GABAergic synapses）等分子通路。研究证实，更高的成瘾严重程度与过度的γ-氨基丁酸能抑制作用相关；通过药物抑制（pharmacological inhibition）实验，我们发现成瘾样表型受代谢物甲基乙二醛（methylglyoxal）调控，该物质是γ-氨基丁酸A型（GABA-A）受体的激动剂。通过分析染色质可及性差异，我们预测了与成瘾样行为相关的上游转录调控因子，并发现不同细胞群体中关键转录因子的调控模式存在不一致。总体而言，本研究全面表征了持续戒断期内杏仁核内细胞类型特异性的转录变化，并基于这些发现确定了一种全新的药物干预（pharmacological intervention）靶点。