Molecular Mechanisms of Cocaine-Induced Alterations in Accumbens AMPA Receptors

描述（由申请人提供）：药物成瘾的特点是即使在长期戒毒后也极易复发。复发脆弱性与突触核突触功能失调有关，包括AMPA谷氨酸受体表达改变。然而，药物诱导的突触可塑性变化的潜在机制尚不完全清楚。最近，细胞粘附分子β 3整合素被确定为在维持含有GluR2亚基的AMPA受体的表面表达中起关键作用。来自我们实验室的数据表明，在可卡因自我给药期间向大鼠慢性内注射β 3整联蛋白调节剂减少了可卡因引发的药物寻求的随后恢复，并防止可卡因诱导的GluR2表面表达减少。目前的建议旨在进一步阐明β 3整联蛋白信号通路，以确定可卡因诱导的AMPA受体变化的分子机制。我推测正常的β 3整合素信号传导被可卡因诱导的基质金属蛋白酶（MMP）过度活性破坏，这导致β 3整合素介导的含GluR2的AMPA受体通过Rap1细胞内信号传导的激活而内吞。具体目标1：在大鼠中使用自我给药模型，我首先计划确定MMP或Rap1抑制剂的内给药核心输注是否减少了已熄灭的可卡因寻求的恢复，如先前对于β 3整联蛋白调节剂所见。具体目标二：使用被发现对减少恢复行为最有效的治疗剂量，我计划下一步评估每种内给药治疗的生化后果（MMP抑制、Rap1抑制或β 3整联蛋白调节）。对该蛋白表达水平的分析将有助于揭示行为效应的潜在机制以及假设途径中组分之间可能的相互作用。这些行为和生化研究的结果将揭示可卡因诱导的谷氨酸传递神经适应的分子机制。 公共卫生相关性：药物成瘾与持久的大脑变化有关，这些变化导致复发的脆弱性增加，即使在长期戒毒之后。这项研究将调查一个分子信号通路，可能是可卡因诱导的突触功能变化的基础，突触核是一种与奖励学习和成瘾密切相关的大脑结构。确定参与成瘾发展的过程可能会导致旨在逆转药物诱导的改变的新的治疗选择。

DESCRIPTION (provided by applicant): Drug addiction is characterized by a high vulnerability to relapse, even following extended drug abstinence. Relapse vulnerability has been linked to dysregulation in nucleus accumbens synaptic function, including altered AMPA glutamate receptor expression. However, the underlying mechanisms of drug-induced changes in accumbens synaptic plasticity are not fully known. Recently, the cell adhesion molecule beta3 integrin was identified as playing a key role in maintaining surface expression of AMPA receptors containing the GluR2 subunit. Data from our laboratory show that chronic intra-accumbens infusion of beta3 integrin modulators to rats during cocaine self-administration reduced subsequent reinstatement of drug-seeking elicited by a cocaine prime and prevented cocaine-induced reductions in GluR2 surface expression. The current proposal is aimed at further elucidating this beta3 integrin signaling pathway to determine the molecular mechanisms of cocaine- induced AMPA receptor changes. I hypothesize that normal beta3 integrin signaling is disrupted by cocaine- induced overactivity of matrix metalloproteinases (MMPs), which causes beta3 integrin-mediated endocytosis of GluR2-containing AMPA receptors via activation of Rap1 intracellular signaling. Specific Aim 1: Using the self-administration model in rats, I first plan to determine whether intra-accumbens core infusions of MMP or Rap1 inhibitors reduce reinstatement of extinguished cocaine-seeking, as seen previously for beta3 integrin modulators. Specific Aim 2: Using the treatment doses found to be most effective for reducing reinstatement behavior, I plan next to evaluate the biochemical consequences of each intra-accumbens treatment (MMP inhibition, Rap1 inhibition, or beta3 integrin modulation). Analyses of accumbens protein expression levels will help reveal the underlying mechanisms of the behavioral effects and possible interactions among components within the hypothesized pathway. Results from these behavioral and biochemical studies will shed light on the molecular mechanisms of cocaine-induced neuroadaptations in accumbens glutamate transmission. PUBLIC HEALTH RELEVANCE: Drug addiction is associated with long-lasting brain changes that cause heightened relapse vulnerability, even after extended drug abstinence. This research study will investigate a molecular signaling pathway that might underlie cocaine-induced changes in synaptic function in nucleus accumbens, a brain structure critically involved in reward learning and addiction. Determining the processes involved in the development of addiction may lead to novel therapeutic options aimed at reversing drug-induced alterations.