Mechanistic studies of phosphodiesterase inhibitors in cocaine addiction

描述（由申请人提供）：可卡因成瘾是一个严重的公共卫生问题。没有FDA批准的药物用于治疗可卡因成瘾。先前的研究表明，磷酸二酯酶-4（PDE-4）抑制剂咯利普兰减少多种药物滥用的成瘾行为在多个行为测定和腹侧被盖区（VTA）是一个主要的网站，介导其行动。考虑到PDE4和非选择性PDE抑制剂在动物研究中改善了衰老相关的代谢表型，并在临床试验中显示出治疗呼吸系统疾病和抑郁症的有效性，这些抑制剂是开发具有潜在健康益处的抗成瘾药物的有希望的候选药物。本项目的目的是研究PDE受体介导的可卡因条件位置偏爱（CPP）和运动敏感化减弱的神经回路和下游信号机制。核心假设是PDE抑制剂通过激活cAMP（Epac）激活的交换蛋白和抑制VTA中的哺乳动物雷帕霉素靶蛋白（mTOR）信号传导来降低可卡因的行为效应。将通过三个特定目的来测试该假设：1）测试PDE抑制剂是否激活VTA多巴胺神经元中的Epac信号传导以减弱可卡因诱导的CPP和运动敏化。在这个目标下，我们将使用设计师受体专门激活的设计师药物（DREADD）技术来询问神经元细胞类型，介导PDE抑制剂的作用。我们将研究VTA中Epac信号传导的中断是否废除PDE抑制剂的行为效应。2)研究PDE抑制剂减弱可卡因CPP的突触机制。在这个目标下，我们将测试的假设，PDE抑制剂诱导长期抑郁样突触修饰，“中和”可卡因诱发的突触增强，并提供了一个潜在的机制，减少可卡因CPP PDE抑制剂诱导。3)测试PDE抑制剂是否通过抑制mTOR信号传导降低可卡因CPP和运动致敏。在此目标下，我们将使用cre-loxP系统在VTA中产生mTOR的条件性敲除，并检查其对可卡因诱导的CPP和PDE抑制剂诱导的行为敏化和行为变化的影响。鉴定下游靶点和介导PDE抑制剂作用的分子机制是将PDE抑制剂"再利用"用于抗成瘾药物的关键第一步。

DESCRIPTION (provided by applicant): Cocaine addiction is a serious public health problem. There are no FDA approved medications for the treatment of cocaine addiction. Previous studies have shown that phosphodiesterase-4 (PDE-4) inhibitor rolipram reduces addictive behavior by multiple drugs of abuse in multiple behavior assays and the ventral tegmental area (VTA) is a primary site that mediates its action. Considering that PDE4 and non-selective PDE inhibitors ameliorate aging-related metabolic phenotypes in animal studies and show effectiveness in treating respiratory diseases and depression in clinical trials, these inhibitors are a promising candidate for developing anti-addiction medications with potential health benefits. The goal of this project is to investigate neural circuits and downstream signaling mechanisms that mediate PDE inhibitor-induced attenuation of cocaine conditioned place preference (CPP) and locomotor sensitization. The central hypothesis is that the PDE inhibitors reduce the behavioral effects of cocaine through activation of exchange proteins activated by cAMP (Epac) and inhibition of the mammalian target of rapamycin (mTOR) signaling in the VTA. The hypothesis will be tested through three Specific Aims: 1) Test if the PDE inhibitors activate Epac signaling in VTA dopamine neurons to attenuate cocaine-induced CPP and locomotor sensitization. Under this Aim, we will use the designer receptors exclusively activated by designer drugs (DREADD) technology to interrogate the neuronal cell-type that mediates the action of PDE inhibitors. We will examine whether disruption of Epac signaling in the VTA abrogates the behavioral effects of the PDE inhibitors. 2) Investigate synaptic mechanisms by which the PDE inhibitors attenuate cocaine CPP. Under this Aim, we will test the hypothesis that the PDE inhibitors induce long-term depression-like synaptic modification, which "neutralizes" cocaine-evoked synaptic potentiation and provides a potential mechanism for the reduction in cocaine CPP induced by PDE inhibitors. 3) Test whether PDE inhibitors reduce cocaine CPP and locomotor sensitization through inhibition of mTOR signaling. Under this Aim, we will use a cre-loxP system to produce conditional knockout of mTOR in the VTA and examine its impact on cocaine-induced CPP and behavioral sensitization and behavioral changes induced by the PDE inhibitors. The identification of downstream targets and molecular mechanisms that mediate the action of the PDE inhibitors is a critical first step toward "repurposing" PDE inhibitors for anti-addiction medications.