VTA Ionotropic Glutamate Receptors in Cocaine Addiction

可卡因成瘾被认为涉及中脑边缘多巴胺神经元的神经可塑性。先前 研究发现，重复的“被动”可卡因给药短暂地增加多巴胺神经元 腹侧被盖区（VTA）的兴奋性，这种作用可能会引起长期的药物敏感性 和其他刺激物引发渴望和复发。一些研究表明，增加多巴胺神经元 兴奋性是由可卡因诱导的AMPA和NMDA的GluR 1和NR 1亚基的上调引起的 谷氨酸受体，而其他人认为这些变化与PKA和PKC/CaMKII介导的 促进AMPA和NMDA受体插入突触膜的磷酸化过程，和 增强受体功能。 我们的初步结果表明，慢性可卡因“自我”管理产生-90%的上升- 在早期（1天）戒断时VTA中GluR 1水平的调节。因此，目标I的研究将进一步 描述慢性可卡因后GluR 1和其他AMPA和NMDA受体亚单位的上调 自身给药，包括PKA和PKC/CaMKII介导的GluR 1和NR 1磷酸化，以及 可卡因戒断中神经适应性变化的持续性。这些研究还将确定是否 被动和自我管理差异调节AMPA和NMDA受体亚单位，以及是否 基于个体差异，变化与“成瘾”与“非成瘾”表型特别相关 可卡因摄入量的最佳水平鉴于腹侧被盖区神经元的功能和解剖异质性，目的II 将测量不同VTA亚区以及多巴胺能和GABA能细胞中GluR 1的上调 慢性可卡因自我管理后。 目的III和IV将确定GuR 1和NR 1上调在成瘾样神经元损伤中的功能作用。 可卡因自我给药的变化，以及对可卡因的直接（短期）和间接（长期）影响 恢复可卡因寻求戒断。在这些研究中，将病毒载体注入VTA， 产生高度局部化的AMPA和NMDA受体亚单位在体内的过度表达之前，行为 试验.显性失活GluR 1和NR 1突变体将决定下调AMPA的作用， NMDA受体介导的兴奋性输入到腹侧被盖区神经元的自我管理和恢复。 类似地，磷酸化抗性突变体将研究PKA和PKC/CaMK II介导的磷酸化的作用。 GluR 1和NR 1磷酸化在成瘾行为调控中的作用。总之，这些研究将测试 假设可卡因诱导的VTA中GluR 1和NR 1的上调有助于成瘾相关的 可卡因自我给药的变化，以及在戒断过程中寻求可卡因的复发倾向。

Cocaine addiction is thought to involve neuroplasticity in mesolimbic dopamine neurons. Previous studies have found that repeated "passive" cocaine administration transiently increases dopamine neuron excitability in the ventral tegmental area (VTA), and this effect may induce long-term sensitization to drugs and other stimuli that trigger craving and relapse. Some studies suggest that increased dopamine neuron excitability is caused by cocaine-induced up-regulation in GluR1 and NR1 subunits of AMPA and NMDA glutamate receptors, while others suggest these changes are related to PKA- and PKC/CaMKII-mediated phosphorylation processes that facilitate AMPA and NMDA receptor insertion into synaptic membranes, and enhance receptor function. Our preliminary results suggest that chronic cocaine "self'-administration produces a -90% up- regulation in GluR1 levels in the VTA at early (1 day) withdrawal. Thus, studies in Aim I will further characterize GluR1 up-regulation and other AMPA and NMDA receptor subunits following chronic cocaine self-administration, including PKA- and PKC/CaMKII-mediated phosphorylation of GluR1 and NR1, and the persistence of neuroadaptive changes in cocaine withdrawal. These studies also will determine whether passive and self-administration differentially regulates AMPA and NMDA receptor subunits, and whether changes are specifically related to "addicted" vs. "non-addicted" phenotypes based on individual differences in preferred levels of cocaine intake. Given functional and anatomical heterogeneity in VTA neurons, Aim II will measure GluR1 up-regulation in distinct VTA subregions, and in dopaminergic and GABAergic cell types, following chronic cocaine self-administration. Aims III and IV will determine the functional role of GuR1 and NR1 up-regulation in addiction-like changes in cocaine self-administration, and both the direct (short-term) and indirect (long-term) effects on reinstatement of cocaine seeking in withdrawal. In these studies, viral vectors will be infused into the VTA to produce highly localized over-expression of AMPA and NMDA receptor subunits in vivo prior to behavioral tests. Dominant negative GluR1 and NR1 mutants will determine the effects of down-regulating AMPA and NMDA receptor-mediated excitatory input to VTA neurons on self-administration and reinstatement. Similarly, phosphorylation-resistant mutants will study the role of PKA- and PKC/CaMKII-mediated phosphorylation of GluR1 and NR1 in regulating addictive behavior. Together, these studies will test the hypothesis that cocaine-induced up-regulation in GluR1 and NR1 in the VTA contributes to addiction-related changes in cocaine self-administration, and the propensity for relapse to cocaine seeking in withdrawal.