Mechanisms underlying opposing neuronal responses to brief vs. prolonged dopamine

神经元对短暂多巴胺和长时间多巴胺反应相反的机制

• 批准号: 8014897
• 负责人: Deborah Jean Baro
• 金额: $ 35.11万
• 依托单位: GEORGIA STATE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-05 至 2012-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8014897
• 关键词: American; Binding; Biochemical; CREB1 gene; Characteristics; Chronic; Cocaine; Confocal Microscopy; Cost of Illness; Crustacea; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cyclic AMP-Responsive DNA-Binding Protein; Dominant-Negative Mutation; Dopamine; Dopamine D1 Receptor; Dopamine D2 Receptor; Dose; Drug abuse; Electrophysiology (science); Global Change; Grant; Hour; Imagery; Ion Channel; Ions; Kv4 channel; Lead; Learning; Life; Measures; Mediating; Membrane; Memory; Modeling; Modification; Molecular; Molecular Biology; Names; Neurons; Pharmaceutical Preparations; Phosphorylation; Potassium; Principal Investigator; Prize; Process; Reporting; Research; Research Priority; Rewards; Signal Transduction; Societies; Synapses; Techniques; Testing; Transcript; addiction; classical conditioning; cocaine use; density; prevent; programs; response; reuptake; tool; transcription factor

DESCRIPTION (provided by applicant): 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 densities 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. One of NIDA's top research priorities is finding drugs to block cocaine's effects. This will require an understanding of the mechanisms by which cocaine acts. Cocaine causes a prolonged exposure of neurons to dopamine, which in turn causes many alterations to neuronal function. This grant aims to understand the mechanisms by which prolonged dopamine alters neuronal function.

药物滥用是一种慢性和毁灭性的疾病，每年给社会造成超过2000亿美元的损失。这个问题很普遍; 2004年，超过3400万美国人报告终身使用可卡因。NIDA的首要研究重点之一是找到阻断可卡因作用的药物，这需要了解成瘾的分子机制。持续使用可卡因导致奖励相关学习的适应不良，以至于药物被视为高于所有其他奖励，尽管有严重的负面后果（成瘾），但仍被强迫性地寻求和使用。皮质醇阻止多巴胺（DA）的再摄取。单剂量的成瘾药物可以提高突触DA数小时。目前尚不清楚[DA]的重复和长期升高如何破坏联想学习和记忆的正常机制。这些过程依赖于离子通过神经元膜中通道的流动（离子电流）;因此，神经元膜中离子通道的密度和特性有助于确定神经元参与学习和记忆机制的能力。已知可卡因和DA都能改变离子电流密度。也许可卡因诱导的学习和记忆畸变是由于DA长期升高导致的离子电流密度的变化。阐明突触DA长期升高导致离子电流密度变化的过程可能会导致成瘾如何篡夺奖励相关的学习和记忆的正常机制的更深层次的认识。瞬时钾电流（IA）对学习和记忆非常重要。Kv 4通道介导IA。使用一个模型电路，甲壳动物幽门网络，我们发现，当DA结合到它的受体，D1和D2，他们产生全球的生化信号，具有不同的影响IA密度在短期和长期。例如，响应于DA的短暂应用，D2受体介导IA密度的增加。另一方面，延长4小时。DA的应用产生D2介导的IA密度的持续降低10-12小时。当DA被移除后该提案重点关注短暂与长期应用DA对IA密度产生相反影响的机制。我们专门测试的假设，DA诱导全局变化[cAMP]，然后改变磷酸化状态的Kv 4通道和一个转录因子命名为CREB。而Kv 4通道的变化是相对短暂的，CREB活性的修改是长期存在的，并导致Kv 4转录本数量的改变。在这里，我们建议使用分子生物学和电生理学技术来测量和相关的全球[cAMP]，IA密度和SHAL转录本数量的变化。此外，药理学工具将用于拮抗或模拟[cAMP]的整体变化，以确定它们是否是IA密度和shal转录本数量变化的基础。此外，显性阴性CREB蛋白的表达和可视化的蛋白激酶A易位使用共聚焦显微镜将有助于确定CREB是否参与介导的长期反应。NIDA的首要研究重点之一是寻找药物来阻断可卡因的作用。这将需要了解可卡因的作用机制。皮质醇导致神经元长时间暴露于多巴胺，这反过来又导致神经元功能的许多改变。该基金旨在了解多巴胺延长改变神经元功能的机制。