Mechanistic studies of phosphodiesterase inhibitors in cocaine addiction

描述(申请人提供)：可卡因成瘾是一个严重的公共卫生问题。目前还没有FDA批准的治疗可卡因成瘾的药物。先前的研究表明，磷酸二酯酶-4(PDE-4)抑制剂Rolipram在多种行为测试中通过滥用多种药物来减少成瘾行为，腹侧被盖区(VTA)是其作用的主要部位。考虑到PDE4和非选择性PDE抑制剂在动物实验中可以改善衰老相关的代谢表型，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潜在候选者。该项目的目标是研究神经回路和下游信号机制，介导PDE抑制剂诱导的可卡因条件性位置偏爱(CPP)减弱和运动敏化。中心假说是，PDE抑制剂通过激活cAMP激活的交换蛋白(EPAC)和抑制VTA中的哺乳动物雷帕霉素靶信号(MTOR)来减少可卡因的行为效应。这一假说将通过三个特定的目的来验证：1)测试PDE抑制剂是否激活VTA多巴胺神经元中的EPAC信号，以减弱可卡因诱导的CPP和运动敏化。在这一目标下，我们将使用由设计药物(DREADD)技术唯一激活的设计受体来询问介导PDE抑制剂作用的神经细胞类型。我们将研究VTA中EPAC信号的中断是否消除了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。在这一目标下，我们将检验这一假说，即PDE抑制剂诱导长时间的抑郁样突触修饰，从而中和可卡因诱导的突触增强，并为PDE抑制剂降低可卡因CPP提供一个潜在的机制。3)检测PDE抑制剂是否通过抑制mTOR信号通路而降低可卡因CPP和运动敏化。在这一目标下，我们将使用cre-loxP系统在VTA中产生条件基因敲除mTOR，并检测其对可卡因诱导的CPP和PDE抑制剂诱导的行为敏化和行为改变的影响。识别下游靶点和介导PDE抑制剂作用的分子机制是将PDE抑制剂重新用于抗成瘾药物的关键的第一步。

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.