背景:物质使用障碍(SUD)的特征是与奖励相关的大脑区域发生长期持续的变化,例如伏隔核(NAc)。以前的工作表明,可卡因暴露会引起广泛的可塑性,NAc中遗传定义的细胞类型;然而,作为对刺激的回应,只有一小部分的神经元是转录活跃的-被称为合奏。这里,我们确定了一个表达Arc的神经元集合,该集合具有独特的募集轨迹,并且在重复后可以控制药物的自我给药,但不是急性的,可卡因暴露。
方法:使用Arc-CreERT2转基因小鼠,我们在可卡因暴露激活的Arc+合奏中表达转基因[急性(1x10mg/kgIP),或重复(10x10mg/kgIP)]。利用遗传,光学,以及生理记录和操纵策略,我们评估了这些合奏对SUD相关行为的贡献。
结果:反复接触可卡因会减少合奏的大小,同时增加对行为的控制。重复可卡因集合中的神经元高度兴奋,其光遗传学激发足以增强。最后,留下重复的可卡因,但不是急性可卡因,合奏削弱了可卡因的自我管理。因此,反复接触可卡因会减少整体的大小,同时增加其对药物强化的贡献。
结论:我们表明,但不是急性的,可卡因暴露会诱导生理上不同的集合,其特征是立即早期基因Arc的表达,具有独特的调节强化行为的能力。
BACKGROUND: Substance use disorder is characterized by long-lasting changes in reward-related brain regions, such as the nucleus accumbens. Previous work has shown that cocaine exposure induces plasticity in broad, genetically defined cell types in the nucleus accumbens; however, in response to a stimulus, only a small percentage of neurons are transcriptionally active-termed an ensemble. Here, we identify an Arc-expressing neuronal ensemble that has a unique trajectory of recruitment and causally controls drug self-administration after repeated, but not acute, cocaine exposure.
METHODS: Using Arc-CreERT2 transgenic mice, we expressed transgenes in Arc+ ensembles activated by cocaine exposure (either acute [1 × 10 mg/kg intraperitoneally] or repeated [10 × 10 mg/kg intraperitoneally]). Using genetic, optical, and physiological recording and manipulation strategies, we assessed the contribution of these ensembles to behaviors associated with substance use disorder.
RESULTS: Repeated cocaine exposure reduced the size of the ensemble while simultaneously increasing its control over behavior. Neurons within the repeated cocaine ensemble were hyperexcitable, and their optogenetic excitation was sufficient for reinforcement. Finally, lesioning the repeated cocaine, but not the acute cocaine, ensemble blunted cocaine self-administration. Thus, repeated cocaine exposure reduced the size of the ensemble while simultaneously increasing its contributions to drug reinforcement.
CONCLUSIONS: We showed that repeated, but not acute, cocaine exposure induced a physiologically distinct ensemble characterized by the expression of the immediate early gene Arc, which was uniquely capable of modulating reinforcement behavior.