Molecular Mechanisms of Cocaine-Induced Alterations in Accumbens AMPA Receptors

描述(申请人提供)：吸毒成瘾的特点是很容易复发，即使在长期戒毒之后也是如此。复发易感性与伏隔核突触功能失调有关，包括AMPA谷氨酸受体表达的改变。然而，药物引起伏隔神经突触可塑性改变的潜在机制尚不完全清楚。最近，细胞黏附分子Beta3整合素被发现在维持含有GluR2亚单位的AMPA受体的表面表达中起关键作用。我们实验室的数据显示，在可卡因自我给药过程中，长期在伏隔内注β3整合素调节剂可以减少可卡因引发的药物寻找的恢复，并阻止可卡因诱导的GluR2表面表达的减少。目前的建议旨在进一步阐明该β3整合素信号通路，以确定可卡因诱导AMPA受体变化的分子机制。我假设正常的β3整合素信号被可卡因诱导的基质金属蛋白酶(MMPs)过度激活所干扰，后者通过激活Rap1细胞内信号导致含有GluR2的AMPA受体的β3整合素介导的内吞。具体目标1：利用大鼠的自我给药模型，我首先计划确定伏隔核内注射基质金属蛋白酶或RAP1抑制剂是否会减少熄灭的可卡因寻求的恢复，就像以前对β3整合素调节剂所看到的那样。具体目标2：使用被发现对减少恢复行为最有效的治疗剂量，接下来我计划评估每种伏隔内治疗的生物化学后果(基质金属蛋白酶抑制、RAP1抑制或β3整合素调节)。对伏隔蛋白表达水平的分析将有助于揭示行为效应的潜在机制，以及假设途径中各成分之间可能的相互作用。这些行为和生化研究的结果将有助于阐明可卡因诱导伏隔核谷氨酸传递的神经适应的分子机制。 公共卫生相关性：吸毒成瘾与长期的大脑变化有关，这种变化会导致复发易感性增加，即使在长期戒毒之后也是如此。这项研究将探讨可卡因诱导伏隔核突触功能改变的分子信号通路，伏隔核是一种关键参与奖赏学习和成瘾的大脑结构。确定与成瘾发展有关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.