Mechanisms underlying increased cocaine self-administration in Npas2 knockout mice

项目总结/摘要 昼夜节律的紊乱不仅是成瘾的常见症状，而且还有助于 物质依赖的发展。然而，昼夜节律失调影响 成瘾在很大程度上是未知的。生物钟基因的突变和多态性已被证明是 增加啮齿类动物的成瘾相关行为，并与物质依赖的脆弱性有关 在人类身上。CLOCK和NPAS 2是分子钟的关键调节因子。NPAS 2类似于CLOCK， 然而，这些蛋白质的结构和功能在表达模式上存在关键差异。时钟 在大脑中普遍表达，而NPAS 2在丘脑核中高度有节奏地表达 (NAc)并且富含表达D1的神经元。我们的实验室发现，当时钟基因的突变增加 可卡因偏好和自我给药，Npas 2敲除（KO）小鼠的可卡因减少 偏好这些结果表明，NPAS 2和CLOCK在调节奖赏相关的 行为。然而，我最近的数据显示，尽管可卡因偏好减少，但Npas 2 KO小鼠 增加可卡因自我管理。而不是衡量可卡因的偏好，这是基于 可卡因的药理学及其快感，自我管理措施，主动，意志，慢性药物 摄入量，以及可卡因的强化和激励特性，以及类似复发的行为。以来 偏好和药物摄入是根本不同的措施，NPAS 2影响的机制 这些与奖励有关的行为可能是独特的。然而，还需要进一步的研究来了解 昼夜节律基因的改变可能会加剧药物摄入。该提案将侧重于确定可能的 在Npas 2 KO小鼠中增加药物摄入的细胞和分子机制。最近我们的实验室发现 NAc中的Npas 2敲低增加了多巴胺能传递和AMPA/NMDAR比率， D1神经元。暴露于可卡因改变了NAc中的多巴胺能传递，这是已知的调节自我调节。 管理和恢复。此外，Npas 2 KO增加NAc中的树突棘密度， 可能会导致这种传播的增加。这些结果表明， 神经传递可能是Npas 2 KO小鼠中可卡因自我给药增加的基础。在这份提案中，我 目的是确定NPAS 2如何调节D1介导的信号传导，以及是否增加了D1介导的信号传导。 NAc有助于增加Npas 2 KO小鼠中的可卡因自我给药。为了理解如何 当Npas 2 KO的信号转导被改变时，我将首先确定Npas 2 KO如何影响细胞结构和靶向RNA NAc D1神经元表达。随后，我将尝试使Npas 2 KO小鼠的自我给药正常化 通过抑制D1 NAc神经元。总之，这些目标将开始确定潜在的细胞和分子 NPAS 2在奖赏中复杂作用的潜在机制。

Project Summary/Abstract Disruptions in circadian rhythms are not only a common symptom of addiction, but also contribute to the development of substance dependence. However, the mechanisms by which circadian dysregulation impacts addiction are largely unknown. Mutations and polymorphisms in circadian clock genes have been shown to augment addiction-related behaviors in rodents and are associated with vulnerability to substance dependence in humans. CLOCK and NPAS2 are key regulators of the molecular clock. NPAS2 is similar to CLOCK in structure and function, however, there are key differences in the expression patterns of these proteins. CLOCK is ubiquitously expressed in the brain, while NPAS2 is highly, rhythmically expressed in the nucleus accumbens (NAc) and is enriched in D1 expressing neurons. Our lab found that while a mutation in the Clock gene increases cocaine preference and self-administration in mice, Npas2 knockout (KO) mice have decreased cocaine preference. These results suggest that NPAS2 and CLOCK play unique roles in regulating reward-related behaviors. However, my recent data show that despite a reduction in cocaine preference, Npas2 KO mice have increased cocaine self-administration. Instead of measuring cocaine preference, which is based on the pharmacology of cocaine and its pleasurable effects, self-administration measures active, volitional, chronic drug intake, as well as the reinforcing and motivational properties of cocaine, and relapse-like behavior. Since preference and drug intake are fundamentally different measures, the mechanisms by which NPAS2 affects these reward-related behaviors are likely unique. However, further research is needed to understand how alterations in circadian genes might be exacerbating drug intake. This proposal will focus on identifying possible cellular and molecular mechanisms underlying increased drug intake in Npas2 KO mice. Recently our lab found that Npas2 knockdown in the NAc increases glutamatergic transmission and AMPA/NMDAR ratio specifically in D1 neurons. Cocaine exposure alters glutamatergic transmission in the NAc and this is known to regulate self- administration and reinstatement. In addition, Npas2 KO increases dendritic spine density in the NAc, which could contribute to this increase in transmission. These results suggest that changes in glutamatergic neurotransmission could underlie increased cocaine self-administration in Npas2 KO mice. In this proposal, I aim to determine how NPAS2 regulates D1 glutamatergic signaling and whether increased transmission in the NAc contributes to increased cocaine self-administration in Npas2 KO mice. In order to understand how glutamatergic signaling is altered, I will first determine how Npas2 KO affects cellular structure and targeted RNA expression in NAc D1 neurons. Subsequently, I will attempt to normalize self-administration in Npas2 KO mice by inhibiting D1 NAc neurons. Together, these aims will begin to identify potential cellular and molecular mechanisms underlying the complicated role of NPAS2 in reward.