Neuronal ensembles of drug context-induced impulsive decision making

描述(申请人提供)：高冲动与可卡因成瘾者的药物依赖、药物复发和治疗失败的脆弱性有关。使用一种新的动物模型，我们的实验室已经证明，值得注意的是，单独暴露在与可卡因配对的环境背景下会产生一种增强的冲动状态，这表现为在与可卡因配对的环境中比在不配对的对照环境中更大的延迟折扣行为(即，选择立即可用的小的奖励而不是具有时间延迟的更大的奖励)[11]。基于更多令人兴奋的初步数据和现有的冲动性文献，拟议的探索性R21项目将检验最重要的假设，即外侧眶前皮质(LOFC)内不同的神经元集合促进，而在初级皮质(PRL)则相反，药物上下文诱导的冲动决策(DCIDM)。此外，DCIDM的双向调节源于这些神经元群中的兴奋性投射神经元和GABA能中间神经元在暴露于可卡因配对的背景下的差异激活。具体目标1将检验这一假设，即LOFC和PRL中的药物上下文激活的神经元集合分别对促进和抑制DCIDM至关重要。实验将使用Daun02的药物遗传学方法，在c-fos-lacZ转基因大鼠的LOFC或PRL内选择性地定点损伤假定的可卡因上下文激活的神经元群。我们将评估这些操作对可卡因配对或非配对对照情境中延迟折扣行为的影响。我们预测，损毁可卡因上下文反应性LOFC神经元群将抑制DCIDM，而损毁可卡因上下文反应性PRL神经元群将增强DCIDM。具体目标2将是表征c-fos-lacZ转基因大鼠中调控DCIDM的神经元集合中药物上下文激活的神经元亚群的表型。我们将使用双标记免疫组织化学结合共聚焦显微镜对Daun02从Aim 1开始在大鼠大脑中保留的Fos/CaMKII和Fos/GAD67免疫反应(IR)细胞体进行定量。我们预测，暴露在可卡因配对环境中会在THLOFC中引起优先的兴奋性神经元激活，在PRL中引起优先的GABA能神经元激活，PRL是感兴趣的神经元集合。这将反映在Daun02诱导的OFC中优先Fos/CaMKII-IR细胞丢失和PRL中优先Fos/GAD67-IR细胞丢失中，在DCIDM测试期间可卡因配对上下文暴露后收集的组织中。总体而言，R21项目将使用一种新的动物模型、最先进的药物遗传学技术和共聚焦显微镜下的双标记免疫组织化学技术来探索新发现的DCIDM现象的神经生物学基础。这一高风险/高收益的提案有可能启动一条新的调查路线，为滥用可卡因对冲动决策的后果提供独到的见解，并为可卡因成瘾治疗的发展提供信息。

DESCRIPTION (provided by applicant): High impulsivity is associated with vulnerability to drug dependence, drug relapse, and treatment failure in cocaine addicts. Using a novel animal model, our laboratory has demonstrated that, remarkably, exposure to a cocaine-paired environmental context alone produces a state of increased impulsivity, indicated by greater delay discounting behavior (i.e., choice of a small immediately available reward over a larger reward available with a time delay) in a cocaine-paired context than in an unpaired control context [11]. Based on additional exciting preliminary data and the existing impulsivity literature the proposed exploratory R21 project will test the overarching hypothesis that distinct neuronal ensembles within the lateral orbitofrontal cortex (lOFC) promote, whereas in the prelimbic cortex (PrL) oppose, drug context-induced impulsive decision making (DCIDM). Furthermore, bidirectional regulation of DCIDM arises from the differential activation of excitatory projection neurons and GABAergic interneurons within these neuronal ensembles upon exposure to the cocaine-paired context. Specific Aim 1 will be to test the hypothesis that drug context-activated neuronal ensembles in the lOFC and PrL are critical for promoting and suppressing DCIDM, respectively. Experiments will use the Daun02 pharmacogenetic method to site-selectively lesion putative cocaine context-activated neuronal ensembles within the lOFC or PrL in c-fos-lacZ transgenic rats. We will evaluate the effects of these manipulations on delay discounting behavior in the cocaine-paired or an unpaired control context. We predict that lesion of cocaine context-reactive lOFC neuronal ensembles will inhibit, whereas lesion of cocaine context-reactive PrL neuronal ensembles will potentiate DCIDM. Specific Aim 2 will be to characterize the phenotype of drug context-activated neuronal subpopulations within the neuronal ensembles that regulate DCIDM in c-fos-lacZ transgenic rats. We will use double-label immunohistochemistry with confocal microscopy to quantify Fos/CaMKII- and Fos/GAD67-immunoreactive (IR) cell bodies spared by Daun02 in the brains of rats from Aim 1. We predict that exposure to a cocaine-paired context elicits preferential excitatory neuronal activation in th lOFC, and preferential GABA-ergic neuronal activation in the PrL, neuronal ensembles of interest. This will be reflected by Daun02-induced preferential Fos/CaMKII-IR cell loss in the OFC and preferential Fos/GAD67-IR cell loss in the PrL, in tissue collected after cocaine-paired context exposure during the DCIDM test. Overall, this R21 project will explore the neurobiological underpinnings of the newly discovered DCIDM phenomenon using a novel animal model, state-of-the-art pharmacogenetic techniques, and double-label immunohistochemistry with confocal microscopy. This high risk/high gain proposal has the potential to initiate a new line of investigation, provide original insight into the consequences o cocaine abuse on impulsive decision making, and inform the development of treatments for cocaine addiction.