Regulation of Cocaine Reward and Reinforcement by MeCP2

描述（由申请人提供）：慢性可卡因滥用是由于持续可卡因诱导的中边缘皮层脑奖励回路内神经元功能适应性改变所致。对可卡因改变这些神经回路功能的分子机制的理解可能会导致开发用于治疗可卡因成瘾的新疗法。这个建议的总体假设是，可卡因通过诱导新的基因产物的转录对行为产生持久的影响，这些新的基因产物改变了NAc神经元的兴奋性和/或突触连接性。我们已经表明，基因操纵甲基DNA结合蛋白MeCP 2在成年纹状体的特定区域的表达调节可卡因和相关的精神兴奋剂安非他明诱导啮齿动物成瘾样行为的能力。此外，我们发现，可卡因诱导磷酸化的MeCP 2 Ser 421（pMeCP 2）选择性的小清蛋白（PV）阳性的快速尖峰GABA能中间神经元（FSI）的NAc。该提案的目的是测试新的假设，即FSI中MeCP 2的磷酸化提供了一种机制，将可卡因暴露与限制可卡因奖励特性的纹状体回路功能的转录依赖性变化联系起来。为了解决这一假设，在目标1中，我们将测试MeCP 2磷酸化对可卡因的奖励和强化特性的后果，通过评估携带突变敲入Mecp 2基因的小鼠中的可卡因自我给药（SA），该突变将Ser 421变为Ala，使MeCP 2在该位点不可磷酸化。在目标2中，我们将检验MeCP 2在NAc中的FSI中起作用以限制可卡因SA的假设。我们将实现这一目标，立体定向注射LoxP条件性病毒到NAC的成年小鼠从一个转基因株，表达Cre重组酶在PV阳性神经元。我们将使用这些病毒来操纵MeCP 2在这些细胞中的表达和磷酸化，作为改变FSI功能的手段，我们将确定这些操纵对可卡因SA的影响。最后，在目标3中，我们将检验pMeCP 2通过调节NAc FSI中即刻早期基因的诱导来调节限制可卡因SA的纹状体可塑性的假设。我们的研究结果将是一个特定的电路为基础的机制，染色质调节蛋白MeCP 2限制可卡因奖励的实验演示。这些研究有望对影响可卡因成瘾易感性的神经生物学机制产生重要的新见解。

DESCRIPTION (provided by applicant): Chronic cocaine abuse arises as a result of persistent cocaine-induced adaptations in the function of neurons within mesolimbocortical brain reward circuits. An understanding of the molecular mechanisms by which cocaine alters the function of these neural circuits may lead to development of novel therapies for the treatment of cocaine addiction. The overall hypothesis of this proposal is that cocaine exerts long-lasting effects on behavior by inducing the transcription of new gene products in the nucleus accumbens (NAc) that change the excitability and/or synaptic connectivity of NAc neurons. We have shown that genetically manipulating the expression of the methyl-DNA binding protein MeCP2 in specific regions of the adult striatum modulates the ability of cocaine and the related psychostimulant amphetamine to induce addictive-like behaviors in rodents. Furthermore, we find that cocaine induces phosphorylation of MeCP2 at Ser421 (pMeCP2) selectively in parvalbumin (Pv)-positive fast-spiking GABAergic interneurons (FSIs) in the NAc. The objective of this proposal is to test the novel hypothesis that phosphorylation of MeCP2 in FSIs provides a mechanism to link cocaine exposure with transcription-dependent changes in striatal circuit function that limit the rewarding properties of cocaine. To address this hypothesis, in Aim 1 we will test the consequences of MeCP2 phosphorylation on the rewarding and reinforcing properties of cocaine by assessing cocaine self-administration (SA) in mice bearing a mutation knocked into the Mecp2 gene that changes Ser421 to Ala, rendering MeCP2 non-phosphorylatable at this site. In Aim 2 we will test the hypothesis that MeCP2 acts in FSIs in the NAc to limit cocaine SA. We will achieve this goal by stereotaxically injecting LoxP-conditional viruses into the NAc of adult mice from a transgenic strain that expresses the Cre recombinase in Pv-positive neurons. We will use these viruses to manipulate MeCP2 expression and phosphorylation in these cells as a means to alter FSI function and we will determine the effects of these manipulations on cocaine SA. Finally in Aim 3 we will test the hypothesis that pMeCP2 regulates a striatal plasticity that limits cocaine SA by modulating the inducibility of immediate-early genes in FSIs of the NAc. The outcome of our study will be the experimental demonstration of a specific circuit-based mechanism by which the chromatin regulatory protein MeCP2 limits cocaine reward. These studies promise to yield significant new insights into the neurobiological mechanisms that impact susceptibility to cocaine addiction.