Molecular mechanisms of neural plasticity in drug addiction

描述(由申请人提供)：在美国，9%的12岁及以上的人被认为滥用一种或多种物质，尽管有严重的负面后果(物质滥用和精神卫生服务管理局，2008年)。人类药物滥用通常遵循禁欲和复发的循环，其持久性可能对临床治疗构成最大的挑战。由于药物诱导的啮齿类动物的敏感化被用来模拟成瘾的持久性，了解影响这种行为的机制以及相关的大脑适应，应该为治疗干预或可能的预防提供目标。最近，有研究表明，慢性可卡因暴露通过依赖环磷酸腺苷(CAMP)抑制一种名为肌细胞增强因子2(MEF2)的转录因子来调节伏隔核(大脑的奖励中心)的脊椎密度。此外，MEF2下调和脊椎上调与预防可卡因诱导的行为敏感化有关(Pulipparacharuvil等人，2008年)。本提案的目标是确定负责MEF2调节的特定信号机制，以及确定涉及可卡因诱导的MEF2调节、树突棘密度和行为敏化的信号机制。具体目的1是阐明cAMP依赖抑制MEF2的信号机制。最初的焦点将是钙调素信号调节因子(RCS)，一种小的神经元磷酸蛋白，在使用RCS基因敲除小鼠培养的神经元进行这一过程中是否需要。基于RNAi的蛋白质替代试验和针对MEF2 Ser408/444的特异性磷酸抗体将被用来测试磷酸化在cAMP对MEF2影响中的功能作用，并将使用一种不依赖钙的CaMK来测试这个蛋白家族的参与。具体目的#2是确定RCS在体内对MEF2的可卡因依赖调节、脊柱上调和行为敏化中的作用。这一目的将在可卡因使用的RCS基因敲除小鼠模型中实现，以确定RCS对可卡因引起的上述每个区域变化的必要性。这些研究的结果综合起来，将有助于阐明cAMP和可卡因如何调节MEF2，并最终阐明这些通路中的信号机制如何有助于药物诱导的脊柱可塑性和行为反应。相关性：众所周知，反复接触滥用药物，如可卡因，会导致大脑结构和功能的变化，这可能与成瘾的持久性有关。这个项目的目标是了解这些变化是如何发生的，这可能会导致潜在的治疗或预防成瘾的目标。

DESCRIPTION (provided by applicant): In the U.S., 9% of individuals age 12 and over are considered abusers of one or more substances despite serious negative consequences (Substance Abuse & Mental Health Services Administration, 2008). Human drug abuse typically follows a cycle of abstinence and relapse, the lasting nature of which poses perhaps the greatest challenge to clinical treatment. Since drug-induced sensitization in rodents is used to model the longevity of addiction, understanding mechanisms influencing this behavior, as well as associated brain adaptations, should suggest targets for therapeutic intervention, or possibly, prevention. Recently, it has been shown that chronic cocaine exposure regulates spine density in the nucleus accumbens, the brain's reward center, via cyclic-adenosine monophosphate (cAMP)-dependent inhibition of a transcription factor known as myocyte enhancer factor 2 (MEF2). Furthermore, MEF2 downregulation and spine upregulation are associated with protection against cocaine-induced behavioral sensitization (Pulipparacharuvil et al., 2008). The goal of the current proposal is to determine specific signaling mechanisms responsible for MEF2 regulation, as well as to determine signaling mechanisms involved in cocaine-induced MEF2 regulation, dendritic spine density and behavioral sensitization. Specific aim #1 is to elucidate signaling mechanisms underlying cAMP-dependent inhibition of MEF2. Initial focus will be on whether regulator of calmodulin signaling (RCS), a small neuronal phosphoprotein, is required for this process using neurons cultured from RCS-knockout mice. RNAi-based protein-replacement assays and specific phospho-antibodies to MEF2 Ser408/444 will be used to test the functional role of phosphorylation in cAMP's effect on MEF2, and a calcium-independent form of CaMK will be used to test the involvement of this protein family. Specific aim #2 is to determine the role of RCS in cocaine-dependent regulation of MEF2, spine upregulaton and behavioral sensitization in vivo. This aim will be carried out in a RCS-knockout mouse model of cocaine use in order to determine the necessity of RCS for cocaine-induced changes in each of these areas. Findings from these studies, taken together, will help elucidate how cAMP and cocaine regulate MEF2, and ultimately, how signaling mechanisms in these pathways may contribute to drug-induced spine plasticity and behavioral responses. Relevance: Repeated exposure to drugs of abuse, such as cocaine, is known to cause changes in brain structure and function that may relate to the longevity of addiction. The goal of this project is to understand how these changes occur, which may lead to targets for potential treatment or prevention of addiction.