Homer-mediated signaling and cocaine addiction

摘要/项目摘要 反复暴露可卡因诱导皮质边缘谷氨酸发生持续性、不适应性改变 传播是上瘾表型的核心。因此，可能的候选分子对 可卡因成瘾的神经病理是调节皮质边缘谷氨酸传递的神经病理。超过了 在过去的5年里，霍默家族的突触后支架蛋白已经成为一个关键的调节因子 可卡因诱导的中皮质边缘谷氨酸的变化和可能与 成瘾的标志性特征的分子基础，如复发。Hmer 1基因的多态是 与人类可卡因成瘾和反复服用可卡因显著相关，包括 过量的可卡因自身给药，改变了中皮质边缘荷马基因和蛋白的表达。 行为遗传学研究表明，可卡因诱导前额叶皮质(PFC)Hmer 2蛋白增加 水平是足够的，而降低伏核(NAC)Hmer 2蛋白水平既是必要的，也是必要的 对于使用地点偏好范式评估的可卡因寻觅行为的表达来说，这是足够的。 该项目将通过对可卡因诱导的作用的功能检查来扩展这些早期数据 可卡因对PFC-NAC谷氨酸投射背侧和腹侧Hmer-2表达的影响 配对线索诱导的药物寻找及其相关变化在即刻、中期或 从过量(40-60毫克/公斤/天)的可卡因摄入量中长期戒断。基于我们之前的 免疫印迹和行为神经遗传学数据推测，过量的可卡因摄入 产生时间依赖性的PFC增加和NAC mGluR-Hmer信号通路的减少 这是长期戒毒期间毒品寻觅加剧的原因。具体目标1 该提案将使用免疫印迹和体内微透析来测试特定的假设，即时间- 戒断过量可卡因自我给药过程中寻求可卡因的依赖性增强 与PFC的时间依赖性增加和NAC-Hmer介导的信号通路减少有关 在背侧皮质边缘环路内，导致皮质边缘谷氨酸异常释放。特定的 AIM 2将使用定点定向病毒介导的基因传递来检查 增强和防止可卡因诱导的可卡因PFC-NAC投射中Hmer 2的变化- 配对线索诱导的寻药和NAC谷氨酸传递。预计，所取得的结果 将大大增加我们对Hmer 2在调节兴奋性谷氨酸传递中的作用的理解 腹侧和背侧皮质边缘亚支与复发率的时间依赖性增加有关 脆弱性。这些知识将指向可卡因诱导的Hmer-2调节的改变 PFC-NAC谷氨酸传递的突触后方面作为关键的神经适应调节 在长期戒断过程中的复发倾向，这与理解成瘾有很高的相关性 神经病理学及其谷氨酸靶向药物治疗。

Abstract/Project Summary Repeated cocaine exposure induces persistent, maladaptive changes in mesocorticolimbic glutamate transmission that are central to an addicted phenotype. Thus, likely molecular candidates contributing to the neuropathology of cocaine addiction are those regulating mesocorticolimbic glutamate transmission. Over the past 5 years, the Homer family of post-synaptic scaffolding proteins has emerged as a critical regulator of cocaine-induced changes in mesocorticolimbic glutamate and behavior that likely have relevance for the molecular underpinnings of hallmark features of addiction, such as relapse. A Homer1 polymorphism is significantly associated with cocaine addiction in humans and repeated cocaine administration, including excessive cocaine self-administration, alters mesocorticolimbic Homer mRNA and protein expression. Behavioral genetic studies indicated that a cocaine-induced increase in prefrontal cortex (PFC) Homer2 protein levels is sufficient, while a reduction in nucleus accumbens (NAC) Homer2 protein levels is both necessary and sufficient, for the expression of cocaine-seeking behavior, as assessed using place-preference paradigms. This project will extend these earlier data through a functional examination of the role for cocaine-induced changes in Homer2 expression within the dorsal and ventral PFC-NAC glutamate projections upon cocaine- paired cue-induced drug-seeking and associated changes in NAC glutamate during immediate, intermediate or protracted withdrawal from a period of excessive (40-60+ mg/kg/day) cocaine intake. Based on our previous immunoblotting and behavioral neurogenetics data, it is hypothesized that that excessive cocaine intake produces a time-dependent increase in PFC and decrease in NAC mGluR-Homer signaling pathways that underlie the intensification of drug-seeking during protracted withdrawal. Specific Aim 1 of this proposal will employ immunoblotting and in vivo microdialysis to test the specific hypothesis that the time- dependent intensification of cocaine-seeking during withdrawal from excessive cocaine self-administration is associated with time-dependent increases in PFC and decreases in NAC Homer-mediated signaling pathways within the dorsal mesocorticolimbic circuit, resulting in abnormal mesocorticolimbic glutamate release. Specific Aim 2 will employ site-directed viral-mediated gene delivery to examine the functional consequences of augmenting and preventing cocaine-induced changes in Homer2 within PFC-NAC projections for cocaine- paired cue-induced drug-seeking and NAC glutamate transmission. It is anticipated that the results obtained will greatly increase our understanding of the role for Homer2 in regulating excitatory glutamate transmission within the ventral and dorsal mesocorticolimbic subcircuits as it relates to time-dependent increases in relapse vulnerability. Such knowledge will point to cocaine-induced alterations in Homer2 regulation of both pre- and post-synaptic aspects of PFC-NAC glutamate transmission as critical neuroadaptations regulating the propensity to relapse during protracted withdrawal, which has high relevance for understanding addiction neuropathology and its treatment with glutamate-targeting pharmacotherapies.