The role of dopamine in modulating relapse-induced transient synaptic plasticity

 描述(由申请人提供)：可卡因导致伏隔核核(NAcore)突触可塑性的持久变化，与复发的脆弱性有关。具体地说，可卡因自身给药会导致树突棘头部直径、AMPA/NMDA比率和基质金属蛋白酶(MMP)活性的持久增加。消失后再次暴露于可卡因条件性刺激可在15分钟内产生进一步的快速、瞬时突触增强(t-SP)，并可用这些测量中的任何一种进行量化。然而，当用非偶发性可卡因注射诱导恢复时，t-SP的时程不同，直到45min才能观察到最大反应。这种差异导致了一种假设，即当线索立即推动药物寻找和t-SP时，当非偶发可卡因启动恢复时，药物最初会抑制药物寻找和t-SP，直到药理效应减弱到阈值以下。一个恢复模型被用来评估线索诱导的可卡因寻求导致可卡因使用之间的这种交互作用，模拟了人类复发的许多重要特征。初步数据显示，意外可卡因逆转了线索诱发的t-SP，停止这种通路可迅速恢复t-SP。可卡因增加突触多巴胺(DA)作为多巴胺转运体的竞争性抑制物，因此推测多巴胺能机制有助于可卡因对线索诱导的t-SP的影响。在这里，研究了可卡因诱导的腹侧被盖区(VTA)DA传递在t-SP逆转中的作用，使用由特制药物(DREADD)和酪氨酸羟基酶-Cre(TH-CRE)转基因大鼠特异激活的病毒设计受体来引入解剖学和细胞类型特异性。为了实现这一目标，候选人将学习体内酶谱以分析基质金属蛋白酶活性和膜片钳电生理学(目标1)，以及使用在F32 NRSA培训中获得的树突棘状分析和颅内显微注射技能。在K99 AIMS中，将描述VTA DA在可卡因诱导的NAcore t-SP逆转中的作用。初步数据显示，在VTA TH细胞中存在GQ-DREADD的可卡因训练大鼠将恢复CNO注射，并将进一步评估这种激活是否同样钝化了CUE诱导的t-SP。我们将研究VTA DA胞体的选择性激活(目标2B)或失活(目标2A)或终端场区域(目标2C)对线索诱导的t-SP和可卡因诱导的t-SP抑制的影响。在R00期间，慢性GQ-DREADD激活和CNO自我给药将被用来测试VTA DA活动是否足以复制由慢性可卡因产生的增强的神经可塑性(目标3)。此外，恢复模型中谷氨酸和DA释放的动态调节将用微透析进行评估(目标4)。这些实验有可能有助于开发旨在逆转可卡因引起的神经生物学改变的新的治疗选择。

 DESCRIPTION (provided by applicant): Cocaine produces enduring alterations in nucleus accumbens core (NAcore) synaptic plasticity associated with relapse vulnerability. Specifically, cocaine self-administration causes enduring increases in dendritic spine head diameter, AMPA/NMDA ratios, and matrix metalloproteinase (MMP) activity. Re-exposure to cocaine- conditioned cues after extinction produces further rapid, transient synaptic potentiation (t-SP) within 15 min that is quantified with any of these measurements. However, when inducing reinstatement with a noncontingent cocaine injection the time course of t-SP differs in that the maximal response is not observed until 45 min. This discrepancy led to the hypothesis that while cues immediately drive forward drug seeking and t-SP, when reinstatement is initiated by noncontingent cocaine, the drug initially suppresses drug seeking and t-SP until pharmacological effects diminish below a threshold. A reinstatement model to evaluate this interaction between cue-induced cocaine seeking leading to cocaine use modeling many important features of human relapse was developed. Preliminary data show that contingent cocaine reverses cue-induced t-SP and discontinuation of this access rapidly restores t-SP. Cocaine increases synaptic dopamine (DA) as a competitive inhibitor of the dopamine transporter, thus dopaminergic mechanisms were hypothesized to contribute to cocaine's effects on cue-induced t-SP. Here, the role of cocaine-induced ventral tegmental area (VTA) DA transmission in t-SP reversal is examined using viral-based designer receptors exclusively activated by designer drugs (DREADD) and tyrosine hydroxylase-Cre (TH-Cre) transgenic rats to introduce anatomical and cell-type specificity. To accomplish this, the candidate will learn in vivo zymography to analyze MMP activity and patch clamp electrophysiology (Aim 1), as well as employ dendritic spine analysis and intracranial microinjection skills acquired during F32 NRSA training. In the K99 aims, the contribution of VTA DA in cocaine-induced reversal of NAcore t-SP will be characterized. Preliminary data show that cocaine-trained rats with Gq-DREADD in VTA TH+ cells will reinstate to a CNO priming injection and it will be further assessed whether this activation likewise blunts cue-induced t-SP. The impact of selective activation (Aim 2B) or inactivation of VTA DA cell bodies (Aim 2A) or terminal field regions (Aim 2C) on cue-induced t-SP and cocaine-induced suppression of t- SP will be examined. During the R00 period, chronic Gq-DREADD activation with CNO self-administration will be used to test the sufficiency for VTA DA activity to reproduce potentiated neuroplasticity produced by chronic cocaine (Aim 3). Furthermore, the dynamic regulation of glutamate and DA release in the reinstatement model will be assessed with microdialysis (Aim 4). These experiments have the potential to contribute to the development of novel therapeutic options aimed at reversing cocaine-induced neurobiological alterations.