Mechanisms underlying opposing neuronal responses to brief vs. prolonged dopamine

药物滥用是一种慢性和破坏性疾病，每年给社会造成2000多亿美元的损失。问题是 可卡因广泛存在；2004年，超过3400万美国人报告终生使用可卡因。NIDA的顶级研究之一 当务之急是寻找阻断可卡因的药物？S的作用，这将需要了解分子 成瘾的机制。持续使用可卡因会导致奖赏相关学习的适应不良 这种药物比所有其他奖励都更受珍视，并受到强制追捧和使用，尽管 负面后果(成瘾)。可卡因阻止多巴胺(DA)的再摄取。单剂成瘾剂 药物可使突触DA升高数小时。目前尚不清楚[DA]反复、延长的海拔高度如何扰乱 联想学习和记忆的正常机制。这种过程依赖于离子的流动。 通过神经细胞膜中的通道(离子电流)；因此，离子的密度和特性 神经元膜上的通道有助于确定神经元S参与机制的能力 学习和记忆。可卡因和多巴胺都能改变离子电流密度。可能是可卡因引起的 学习和记忆的异常是由于长时间延长导致的离子电流密度的变化。 地方检察院的高程。阐明突触DA长时间升高导致脑内 离子电流密度可能导致对成瘾如何篡夺正常机制的更深层次的理解 奖励相关的学习和记忆。 瞬时钾电流(IA)对学习和记忆具有重要作用。Kv4通道介导IA。 利用甲壳动物幽门网络的模型电路，我们发现当DA与其受体D1和D2结合时， 它们产生的全球生化信号在短期和长期对IA密度有不同的影响。 例如，对短暂的DA应用作出反应，D2受体介导IA密度的增加。论 另一方面，延长了4小时。DA的应用导致D2介导的IA浓度持续下降10-12 小时。在地方检察官被撤职之后。这一建议着眼于(S)短暂与持久的机制 DA的应用对IA浓度产生相反的影响。我们专门测试了DA诱导的假设 [cAMP]的全局变化，进而改变Kv4通道和转录的磷酸化状态 名为CREB的因子。尽管Kv4通道的变化相对短暂，但CREB的修改 活性是长期存在的，并导致Kv4转录本数量的变化。在这里，我们建议使用分子 生物学和电生理学技术测量和关联全球[cAMP]、IA密度和 沙尔成绩单编号。此外，还将使用药理工具来对抗或模仿全球变化 [cAMP]，以确定它们是否是IA密度和SHAL转录本数量变化的基础。另外， 显性负性CREB蛋白的表达及蛋白激酶A易位的研究 共聚焦显微镜将有助于确定CREB是否参与调节长期反应。

Drug abuse is a chronic and devastating disease, costing society over 200 billion per year. The problem is widespread; in 2004, over 34 million Americans reported lifetime use of cocaine. One of NIDA's top research priorities is finding drugs to block cocaine?s effects, which will require an understanding of the molecular mechanisms of addiction. Persistent use of cocaine leads to maladaptations in reward-related learning such that the drug is prized above all other rewards, and is compulsively sought after and used, despite severe negative consequences (addiction). Cocaine prevents dopamine (DA) reuptake. A single dose of an addictive drug can elevate synaptic DA for hours. It is not clear how repeated, prolonged elevations in [DA] disrupt the normal mechanisms of associative learning and memory. Such processes depend upon the flow of ions through channels in the neuronal membrane (ion currents); therefore, the densites and characteristics of ion channels in the neuronal membrane help to determine the neuron?s capacity to engage in mechanisms of learning and memory. Both cocaine and DA are known to alter ion current densities. Perhaps cocaine-induced aberrations in learning and memory are due to changes in ion current densities resulting from prolonged elevations in DA. Elucidating the processes by which prolonged elevations in synaptic DA lead to changes in ion current densities may lead to a deeper appreciation for how addiction usurps the normal mechanisms of reward related learning and memory. The transient potassium current (IA) is important for learning and memory. Kv4 channels mediate IA. Using a model circuit, the crustacean pyloric network, we found that when DA binds to its receptors, D1 and D2, they produce global biochemical signals that have different effects on IA density over the short- and long-term. For example, in response to a brief application of DA, D2 receptors mediate an increase in IA density. On the other hand, a prolonged 4hr. application of DA produces a D2 mediated, persistent decrease in IA density 10-12 hrs. after DA has been removed. This proposal focuses on the mechanism(s) by which brief versus prolonged applications of DA produce opposing effects on IA density. We specifically test the hypothesis that DA induces global changes in [cAMP] that then alter the phosphorylation state of both Kv4 channels and a transcription factor named CREB. Whereas changes in Kv4 channels are relatively short-lived, modifications in CREB activity are long-lived and result in alterations in Kv4 transcript number. Here we propose to use molecular biology and electrophysiology techniques to measure and correlate changes in global [cAMP], IA density and shal transcript number. Furthermore, pharmacological tools will be used to antagonize or mimic global changes in [cAMP] to determine if they underlie the changes in IA density and shal transcript number. Additionally, expression of a dominant-negative CREB protein and visualization of protein kinase A translocation using confocal microscopy will help to determine if CREB is involved in mediating the long-term response.