Chronic alcohol drinking modulates synchrony between midbrain gene transcription and long-lasting changes in dopamine terminal and opioid function in macaques. Chronic alcohol drinking modulates synchrony between midbrain gene transcription and long-lasting changes in dopamine terminal and opioid function in macaques

Alcohol use disorder is marked by disrupted behavioral and emotional states which can persist into abstinence. The enduring synaptic alterations that remain despite the absence of alcohol are of interest for interventions to prevent relapse. 28 male rhesus macaques underwent over 20 months of alcohol drinking interspersed with three 30-day forced abstinence periods. After the last abstinence period, we paired ex vivo voltammetry in nucleus accumbens slices with RNA-sequencing of the ventral tegmental area. We found persistent augmentation of dopamine transporter function, kappa opioid receptor sensitivity, and dynorphin release – all inhibitory regulators which act to decrease extracellular dopamine. Surprisingly, though transcript expression was not altered, the relationship between gene expression and functional readouts of these encoded proteins was highly dynamic and altered by drinking history. Therefore, the long-lasting synaptic impact of alcohol use suggests that assessment of transcript-function relationships may provide avenues for precision therapeutics targeted to specific synaptic pathophysiologies. Overall design: We paired a model of chronic voluntary alcohol (ethanol) drinking and protracted abstinence with within-subject measures of dopamine terminal function and assessment of gene transcription. In an effort to maximize translational relevance and implications of gene expression quantification, rhesus macaque (macaca mulatta) subjects were used, because of the genetic and behavioral diversity in the model that mirrors individual differences in human drinkers(Grant et al., 2008), as well as the homology to humans in genetic sequence(Gibbs et al., 2007) and neural circuit architecture(Balsters et al., 2020; Haber & Knutson, 2010). Following an induction protocol, subjects were allowed to self-administer alcohol under continuous access conditions for 12 months, followed by three one-month abstinence periods interspersed with three-month periods of re-access to alcohol. At the end of the third and final abstinence period, real-time dopamine release kinetics and inhibitory regulation by axonal KORs were measured directly via ex vivo fast-scan cyclic voltammetry in the NAc of 28 rhesus macaques (17 alcohol drinkers, 11 calorically-yoked or housing controls). Bulk RNA-sequencing of the VTA taken from the same subjects was used to measure gene expression upstream of dopamine terminals.

酒精使用障碍（Alcohol use disorder）以会持续至戒断阶段的行为与情绪状态紊乱为核心特征。即便在停止饮酒后仍长期存在的突触改变，是预防复吸干预策略的重要研究靶点。本研究纳入28只雄性恒河猴，使其接受超过20个月的饮酒造模，期间穿插三次为期30天的强制戒断阶段。末次戒断阶段结束后，我们联合采用伏隔核（nucleus accumbens）脑片离体伏安法检测与腹侧被盖区（ventral tegmental area）的RNA测序（RNA-sequencing）分析。
研究结果显示，多巴胺转运体功能、κ阿片受体敏感性以及强啡肽释放均出现持续性增强——上述三者均为降低胞外多巴胺水平的抑制性调控因子。令人意外的是，尽管转录本表达未发生显著改变，但基因表达与这些编码蛋白的功能读数之间的关联呈现高度动态性，且受个体饮酒史的显著影响。因此，酒精使用带来的持久突触效应提示，对转录-功能关联的评估或许可为靶向特定突触病理的精准治疗提供全新思路。
总体实验设计：本研究将慢性自愿饮酒（乙醇）与长期戒断的动物模型，与多巴胺能末梢功能的受试者内检测以及基因转录评估相结合。为最大化基因表达定量的转化研究相关性，本研究选用恒河猴（Macaca mulatta）作为受试对象：一方面，该模型的遗传与行为多样性可模拟人类饮酒者的个体差异（Grant et al., 2008）；另一方面，其基因序列（Gibbs et al., 2007）与神经环路结构（Balsters et al., 2020; Haber & Knutson, 2010）均与人类高度同源。受试对象先接受诱导方案，随后可在连续摄入条件下自主摄取酒精12个月，之后经历三次为期1个月的戒断阶段，每次戒断后均穿插3个月的酒精复饮阶段。在第三次即末次戒断阶段结束后，我们通过28只恒河猴（17只酒精饮服组，11只热量配对饲养对照组或饲养对照组）的伏隔核脑片离体快速扫描循环伏安法，直接检测实时多巴胺释放动力学以及轴突κ阿片受体介导的抑制调控。同时，采集同一受试对象的腹侧被盖区组织进行批量RNA测序（bulk RNA-sequencing），以分析多巴胺能末梢上游的基因表达水平。