The reinforcing efficacy of cocaine is largely determined by its capacity to inhibit the dopamine transporter (DAT), and emerging evidence suggests that differences in cocaine potency are linked to several symptoms of cocaine use disorder. Despite this evidence, the neural processes that govern cocaine potency in vivo remain unclear. In male rats, we used chemogenetics with intra-VTA microinfusions of the agonist clozapine-n-oxide to bidirectionally modulate dopamine neurons. Using ex vivo fast scan cyclic voltammetry, pharmacological probes of the DAT, biochemical assessments of DAT membrane availability and phosphorylation, and cocaine self-administration, we tested the effects of chemogenetic manipulations on cocaine potency at distal DATs in the nucleus accumbens as well as the behavioral economics of cocaine self-administration. We discovered that chemogenetic manipulation of dopamine neurons produced rapid, bidirectional modulation of cocaine potency at DATs in the nucleus accumbens. We then provided evidence that changes in cocaine potency are associated with alterations in DAT affinity for cocaine and demonstrated that this change in affinity coincides with DAT conformation biases and changes in DAT phosphorylation state. Finally, we showed that chemogenetic manipulation of dopamine neurons alters cocaine consumption in a manner consistent with changes in cocaine potency at distal DATs. Based on the spatial and temporal constraints inherent to our experimental design, we posit that changes in cocaine potency are driven by alterations in dopamine neuron activity. When considered together, these observations provide a novel mechanism through which GPCRs regulate cocaine's pharmacological and behavioral effects.

SIGNIFICANCE STATEMENT Differences in the pharmacological effects of cocaine are believed to influence the development and progression of cocaine use disorder. However, the biological and physiological processes that determine sensitivity to cocaine remain unclear. In this work, we use a combination of chemogenetics, fast scan cyclic voltammetry, pharmacology, biochemistry, and cocaine self-administration with economic demand analysis to demonstrate a novel mechanism by which cocaine potency is determined in vivo. These studies identify a novel process by which the pharmacodynamics of cocaine are derived in vivo, and thus this work has widespread implications for understanding the mechanisms that regulate cocaine consumption across stages of addiction.

可卡因的增强功效在很大程度上取决于其抑制多巴胺转运蛋白（DAT）的能力，新兴证据表明，可卡因效能的差异与可卡因使用障碍的几种症状有关。尽管有这些证据，在体内控制可卡因效力的神经过程仍不清楚。在雄性大鼠中，我们使用激动剂氯氮平正氧化物的VTA内微输注进行化学生成，以双向调节多巴胺神经元。离体使用快速扫描循环伏安法，DAT的药理学探针，DAT膜可利用性和磷酸化的生化评估以及可卡因的自我给药，我们测试了化学操作对远端伏隔核中DAT的可卡因效价的影响以及行为经济学可卡因自我管理。我们发现，多巴胺神经元的化学发生操纵在伏伏核中的DAT处产生可卡因效价的快速，双向调节。然后，我们提供了可卡因效价变化与DAT对可卡因亲和力变化相关的证据，并证明了这种亲和力变化与DAT构象偏差和DAT磷酸化状态的变化相吻合。最后，我们发现，多巴胺神经元的化学发生操纵改变了可卡因的消耗，其方式与远端DAT处可卡因效价的变化一致。基于我们的实验设计固有的时空限制，我们认为可卡因效能的变化是由多巴胺神经元活性的改变所驱动的。综合考虑，这些观察结果提供了一种新颖的机制，GPCR通过这种机制调节可卡因的药理和行为作用。

重要声明据认为，可卡因药理作用的差异会影响可卡因使用障碍的发生和发展。但是，决定对可卡因敏感性的生物学和生理过程仍不清楚。在这项工作中，我们结合使用了化学药理学，快速扫描循环伏安法，药理学，生物化学和可卡因自我管理与经济需求分析，以证明一种在体内确定可卡因效价的新机制。这些研究确定了可卡因在体内衍生的药效学的新过程，因此这项工作对于理解调节成瘾各个阶段可卡因消耗的机制具有广泛的意义。