Mechanisms of Higher-Order Learning in the NAc Impaired by Cocaine Exposure

描述（由申请人提供）：药物成瘾是一种慢性复发性疾病，通常对成瘾者和整个社会产生破坏性后果。新出现的证据表明，这种吸毒和复吸循环的一个可能原因可能集中在认知障碍上。长期暴露于可卡因等滥用药物可通过破坏对认知过程至关重要的边缘结构（如基底外侧杏仁核（BLA）和BLA投射的靶点-丘脑核（NAc））中的神经编码，对一般学习和执行功能产生有害影响。事实上，已知相同的回路对于支持正常（未用药）动物的简单和更认知的高阶学习至关重要。因此，了解这个回路中的正常神经处理以及它如何被重复的可卡因体验改变，对于了解成瘾的一些关键组成部分至关重要，并为可能的治疗提供潜在的治疗途径。在这里，我假设，正常的学习的特点是由BLA输入NAc神经元的多巴胺能（DA能）输入所产生的腹侧被盖区（VTA）调制的相互作用。在重复的可卡因暴露之后，该回路将被破坏，其特征在于向NAc的BLA输入不足和DA信号不足。这种功能障碍将阻止任务相关表征的正常编码，从而损害行为。在辅导K99阶段，我将使用补充技术彻底探索此功能电路。首先，我将使用快速扫描循环伏安法（FCSV）在大鼠中表征DA信号，同时执行二阶巴甫洛夫学习任务，有和没有可卡因自我管理的历史。接下来，我将学习光遗传学技术，并将其应用于TH：：Cre大鼠的转基因系，这将允许VTA中的DA神经元的特异性靶向。有了这项技术，我将能够操纵特定于VTA-NAc通路的DA释放，从而能够观察DA释放的短暂停顿是否足以阻止正常动物的学习，以及DA的短暂爆发是否足以挽救认知功能。在我的独立R 00阶段，我将探索BLA的贡献，这个系统的特点BLA神经编码与体内电生理学的二阶任务的大鼠与可卡因的经验或轭控制的历史。最后，我将使用该实验的数据来观察对NAc选择性的BLA传入的光学抑制是否能够改变 正常动物的学习，但恢复功能的历史，可卡因自我管理的大鼠。两者合计，这个建议将提供一个彻底的表征反复可卡因暴露后的BLA-NAc-VTA神经回路，使用高阶学习任务来解析特定的认知缺陷。

DESCRIPTION (provided by applicant): Drug addiction is a chronically relapsing disorder that often has devastating consequences for the addicted person and society as a whole. Emerging evidence suggests that one possible reason for this cycle of drug taking and relapse may center on cognitive impairments. Chronic exposure to drugs of abuse like cocaine can have deleterious effects on general learning and executive functions by disrupting neural encoding in limbic structures critical for cognitive processes such as the basolateral amygdala (BLA) and a target of BLA projections, the nucleus accumbens (NAc). Indeed, this same circuit is known to be critical for supporting both simple and more cognitive higher-order learning in normal (drug-na¿ve) animals. Thus, understanding the normal neural processing in this circuit and how it is altered by repeated cocaine experience will be essential for understanding some of the critical components of addiction and provide potential therapeutic avenues for possible treatments. Here, I hypothesize that normal learning is characterized by the interaction of BLA input to NAc neurons which are modulated by dopaminergic (DAergic) inputs arising from the ventral tegmental area (VTA). Following repeated cocaine exposure, this circuit will be disrupted, characterized by poor BLA input to NAc and impoverished DA signaling. This dysfunction will prevent the normal encoding of task-relevant representations and consequently impair behavior. During the mentored K99 phase, I will thoroughly explore this functional circuit using complementary techniques. First, I will characterize DA signaling using fast-scan cyclic voltammetry (FCSV) in rats with and without a prior history of cocaine self-administration while performing a second-order Pavlovian learning task. Next, I will learn optogenetic techniques and apply them in a transgenic line of TH::Cre rats which will allow for specific targeting of DA neurons in VTA. With this technique, I will be able to manipulate DA release specific to the VTA-NAc pathway, allowing the ability to see whether brief pauses in DA release are sufficient to block learning in normal animals, and if transient bursts of DA are sufficient to rescue cognitive function. In my independent R00 phase, I will explore the contributions of the BLA to this system by characterizing BLA neural encoding with in vivo electrophysiology of the second- order task in rats with a history of cocaine experience or yoked controls. Finally, I will use data from that experiment to see whether optical inhibition of BLA afferents selective to the NAc is able to alter learning in normal animals, but restore function in rats with a history of cocaine self-administration. Taken together, this proposal will provide a thorough characterization of the BLA-NAc-VTA neural circuit after repeated cocaine exposure, using a higher-order learning task to parse specific cognitive deficits.