A novel and powerful C. elegans behavioral model of addiction

描述(申请人提供)：毒瘾是一种严重且代价高昂的疾病，人们对此知之甚少，几乎没有有效的治疗方法。尽管动物模型已经开始提供有关成瘾的神经生物学某些方面的重要信息，但对成瘾的基本分子基础的理解仍然难以捉摸。对无脊椎动物的基础研究在揭示学习和记忆等复杂行为的潜在机制方面取得了突破性的发现。最近的研究表明，在哺乳动物中定义药物奖励的相同基本类型的行为在无脊椎动物(小龙虾、苍蝇、c-elegans)中也很明显。线虫是研究人类行为神经生物学基础的极佳模型：一个保守得令人惊讶的、易于操作的全序列基因组；一个完整的神经解剖系统；以及快速生成数据所需的较短的世代时间和较低的维护成本，而成本仅为许多其他生物的一小部分。线虫表现出对各种精神活性药物的运动和浓度依赖的自我暴露，包括可卡因、甲基苯丙胺、乙醇和咖啡因。我们发现，在药物预暴露后，它们还表现出敏化、耐受、交叉敏化和交叉耐受。此外，我们最近报道，线虫显示出对以前与可卡因或甲基苯丙胺配对的线索(盐)的条件性偏好，这类似于在哺乳动物模型中发现的药物奖励。总之，这些数据表明线虫可以作为一个很好的行为模型系统来研究药物滥用，具有巨大的潜力来揭示成瘾的潜在分子基础。然而，需要明确的行为证据来完全建立线虫模型，并确认到目前为止观察到的现象与哺乳动物的发现一致。目前的应用将系统地检测对先前与可卡因或甲基苯丙胺相关的线索的线索条件偏好反应(CR)，以确定哺乳动物中存在的一些关键特征是否也存在于线虫中。我们将确定线虫对刺激物的CR是否表现为持续、消亡和恢复，以及它是否受到条件化试验频率、药物预暴露和/或食物限制的影响。所有这些都是 特征是哺乳动物药物奖励模型中的重要因素，预计线虫也会出现这种情况。此外，我们还建议缩减行为分析以在六孔培养板中进行，以便能够使用线虫完全客观、高通量地测量药物偏好和线索-CRS。后续研究将测试哺乳动物同源基因缺陷的突变线虫菌株，这些突变菌株已被证明将线索-CRS与滥用药物联系起来，并将利用药理学和/或RNAi技术在野生型蠕虫中证实这一发现。线虫成瘾行为新模型的建立将是该领域的一项变革性进展。未来的研究将利用研究支撑线虫这些行为的机制的巨大优势。随着寻找新的分子靶点的前景，以及该模型未来在药物开发中筛选化合物的应用，该项目对人类药物成瘾的治疗具有巨大的潜在影响。

DESCRIPTION (provided by applicant): Drug addiction is a serious and costly disorder that is poorly understood with few effective treatments. Although animal models have begun to provide important information about some aspects of the neurobiology of addiction, an understanding of the basic molecular foundations of addiction remains elusive. Basic research with invertebrates has provided ground-breaking discoveries in uncovering the underlying mechanisms of behaviors as complex as learning and memory. Recent work indicates that the same basic types of behavior that define drug reward in mammals are also evident in invertebrates (crayfish, flies, c-elegans). C. elegans is an excellent model to study the neurobiological basis o human behavior with: a surprisingly conserved, fully sequenced genome that can be easily manipulated; a completely mapped neuroanatomical system; and a short generation time with low maintenance costs for fast generation of data at a fraction of the cost of many other organisms. C. elegans demonstrate movement toward, and concentration- dependent self-exposure to, various psychoactive drugs including cocaine, methamphetamine, ethanol and caffeine. We have found that they also show sensitization, tolerance, cross-sensitization, and cross tolerance after drug pre-exposure. In addition, we have recently reported that C. elegans display a conditioned preference for cues (salts) that had previously been paired with cocaine or methamphetamine which is analogous to findings in mammalian models of drug reward. Together these data indicate that C. elegans can serve as an excellent behavioral model system to study drugs of abuse with tremendous potential to uncover the underlying molecular foundations of addictions. However, clear behavioral evidence is needed to fully establish the C. elegans model and confirm that the phenomena observed thus far are consistent with findings in mammals. The current application will systematically examine the cue-conditioned preference response (CR) to cues previously associated with cocaine or methamphetamine to determine if some key characteristics present in mammals are also present in C. elegans. We will determine if the CR to stimulants in C. elegans shows persistence, extinction, and reinstatement, and if it i affected by conditioning trial frequency, drug pre- exposure, and/or food restriction. All of these characteristics are important factors in models of drug reward in mammals and are expected to also be present in C. elegans. In addition, we also propose to scale-down the behavioral assays to conduct them in six-well plates to enable fully objective, high throughput measurements of drug preference and cue-CRs using C. elegans. Follow-up studies would test mutant C. elegans strains with deficits in homologous genes in mammals that have been shown to mediate cue-CRs to drugs of abuse, and findings would be confirmed in wild-type worms using pharmacology, and/or RNAi technology. The establishment of a new behavioral model of addictions in C. elegans would be a transformational advancement in the field. Future studies would leverage the tremendous advantages of studying the mechanisms that underpin these behaviors in C. elegans. With the prospect of identifying new molecular targets, and the future application of this model to screen compounds for medications development, this project has a tremendous potential impact for the treatment of human drug addiction.