Department of Neurobiology and Anatomy, Drexel University College of Medicine, Philadelphia, Pennsylvania 19129.
National Institute on Drug Abuse, Integrative Neuroscience Research Branch, Neuronal Networks Section, Baltimore, Maryland 21224.
J Neurosci. 2020 Nov 4;40(45):8767-8779. doi: 10.1523/JNEUROSCI.0894-20.2020. Epub 2020 Oct 12.
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 remain unclear. In male rats, we used chemogenetics with intra-VTA microinfusions of the agonist clozapine-n-oxide to bidirectionally modulate dopamine neurons. Using 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. 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 These studies identify a novel process by which the pharmacodynamics of cocaine are derived , and thus this work has widespread implications for understanding the mechanisms that regulate cocaine consumption across stages of addiction.
可卡因的强化效果在很大程度上取决于其抑制多巴胺转运体（DAT）的能力，新出现的证据表明，可卡因效力的差异与可卡因使用障碍的几个症状有关。尽管有这些证据，但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 VTA 内氯氮平-氧化物激动剂的化学遗传学方法来双向调节多巴胺神经元。使用快速扫描循环伏安法、DAT 的药理学探针、DAT 膜可用性和磷酸化的生化评估以及可卡因自我给药，我们测试了化学遗传学操作对伏隔核中远端 DAT 中可卡因效力的影响，以及可卡因自我给药的行为经济学。我们发现，多巴胺神经元的化学遗传学操作可快速双向调节伏隔核中 DAT 对可卡因的效力。然后，我们提供了证据表明，可卡因效力的变化与 DAT 对可卡因亲和力的变化有关，并证明这种亲和力的变化与 DAT 构象偏向和 DAT 磷酸化状态的变化有关。最后，我们表明，多巴胺神经元的化学遗传学操作以与远端 DAT 中可卡因效力变化一致的方式改变可卡因的消耗。基于我们实验设计固有的空间和时间限制，我们假设可卡因效力的变化是由多巴胺神经元活动的改变驱动的。综合考虑这些观察结果，为 GPCR 调节可卡因的药理学和行为学效应提供了一种新的机制。可卡因的药理学效应的差异被认为会影响可卡因使用障碍的发展和进展。然而，决定对可卡因敏感性的生物和生理过程仍不清楚。在这项工作中，我们使用化学遗传学、快速扫描循环伏安法、药理学、生物化学和可卡因自我给药与经济需求分析相结合，证明了一种新的机制，通过该机制确定可卡因的效力。这些研究确定了一种新的可卡因药效学产生的过程，因此，这项工作对理解调节可卡因消费的机制具有广泛的意义，这些机制跨越了成瘾的各个阶段。
