Dopamine Release Regulation by Co-Released Glutamate and GABA

描述（由申请人提供）：递质多巴胺（DA）对动机、奖励、运动和认知至关重要。起源于腹侧被盖区（VTA），中边缘DA通路投射到伏隔核（NAc）核心和壳，在那里DA传递有助于食物和药物的奖励作用，并促进目标导向行为和奖励相关学习。与中边缘系统并行，黑质纹状体DA通路起源于黑质致密部（SNc），并投射到尾状壳核（CPu）。这条路径有助于动机行为和运动，并涉及驱动行为从目标导向和故意转变为自动和强迫性。鉴于这些通路的关键作用，DA传递功能障碍在神经精神疾病中起着关键作用，包括精神兴奋剂药物成瘾和帕金森病的运动缺陷。阐明这些疾病的病因，并开发相应的治疗方法，需要了解控制DA释放的因素。通常认为，DA信号仅受DA神经元放电速率和模式的控制，整个纹状体的胞外DA浓度（[DA]o）的变化均呈活动依赖性。然而，事实并非如此：使用快速扫描循环伏安法（FCV）的研究表明，DA释放在纹状体内受到局部调节，在体内和离体脑切片中检测到时间和空间离散的[DA]o瞬态。初步数据表明，纹状体DA轴突共同释放的谷氨酸和GABA介导了动态局部DA释放调控的新来源。本项目将在DA神经元中表达通道视紫红质2 （ChR2）的小鼠离体片中，确定共同释放的谷氨酸和GABA对NAc轴突DA释放（Aim 1）和CPu （Aim 2）以及VTA和SNc体树突DA释放（Aim 3）的自我调节作用。后续研究将使用免疫电子显微镜评估纹状体DA轴突上谷氨酸和GABA受体亚基的存在。根据初步数据显示，单次可卡因注射24小时后，体外切片纹状体DA释放的AMPA受体依赖性调节增强，每个目标将包括检查急性可卡因暴露对DA释放调节的影响。总的来说，这个项目将定义共同释放的谷氨酸和GABA在塑造DA神经元活动的变化如何转化为DA释放中的作用，以及这种调节如何被可卡因破坏。

DESCRIPTION (provided by applicant): The transmitter dopamine (DA) is critical for motivation, reward, movement, and cognition. Originating in the ventral tegmental area (VTA), the mesolimbic DA pathway projects to the nucleus accumbens (NAc) core and shell where DA transmission contributes to the rewarding effects of food and drugs, and promotes goal- directed behavior and reward-related learning. Operating in parallel with the mesolimbic system, the nigrostriatal DA pathway originates in the substantia nigra pars compacta (SNc) and projects to the caudate- putamen (CPu). This pathway contributes to motivated behavior and movement, and is involved in driving behaviors that have transitioned from goal-directed and intentional to automatic and compulsive. Given the key roles of these pathways, dysfunction of DA transmission plays a key role in neuropsychiatric disorders including addiction to psychostimulant drugs and the motor deficits of Parkinson's disease. Elucidating causal factors in these disorders, and developing corresponding treatments, requires an understanding of factors that govern DA release. It is often assumed that DA signaling is governed solely by DA neuron firing rate and pattern, with homogeneous activity-dependent changes in extracellular DA concentration ([DA]o) throughout the striatum. However, this is not the case: studies using fast-scan cyclic voltammetry (FCV) show that DA release is regulated locally within the striatum, with temporally and spatially discrete [DA]o transients detected in vivo and in ex vivo brain slices. Preliminary data suggest that a novel source of dynamic local DA release regulation is mediated by glutamate and GABA that are co-released from striatal DA axons. This project will determine autoregulatory roles of co-released glutamate and GABA on axonal DA release in NAc (Aim 1) and CPu (Aim 2), and somatodendritic DA release in VTA and SNc (Aim 3), in ex vivo slices from mice that express channelrhodopsin 2 (ChR2) in DA neurons. Companion studies will assess the presence of glutamate and GABA receptor subunits on striatal DA axons using immuno-electron microscopy. Based on preliminary data showing enhanced AMPA receptor-dependent regulation of striatal DA release in ex vivo slices 24 h after a single cocaine injection, each aim will include examination of the effect of acute cocaine exposure on DA release regulation by co-released transmitters. Overall, this project will define the roles of co-released glutamate and GABA in sculpting how changes in DA neuron activity translate into DA release, and how this regulation can be disrupted by cocaine.