Functional properties of dopamine and glutamate cotransmission in the nucleus accumbens

 描述（由申请人提供）：成瘾性药物的增强特性是由于其对中脑边缘多巴胺系统的影响，该系统从腹侧被盖区投射到丘脑核。多巴胺在调节到中型多棘神经元的多巴胺能输入中起着中心作用，中型多棘神经元是延髓核的主要输出神经元。最近的研究表明，多巴胺神经元除了正常释放多巴胺外，还在丘脑核中释放谷氨酸。由于谷氨酸在丘脑核中的传递在长期暴露于滥用药物时发生改变，因此了解多巴胺末梢谷氨酸的释放是如何调节的至关重要。先前的研究工作使用电生理学来测量谷氨酸介导的突触后电流，使用电化学来测量多巴胺的细胞外浓度。然而，目前还不清楚电化学测量的细胞外多巴胺是否是驱动突触多巴胺受体激活的多巴胺池。我们最近描述了一种新的方法来测量突触多巴胺传输使用G蛋白激活内向整流钾（GIRK）通道的过表达。由于内源性D2受体有效地耦合到这些GIRK通道，外向钾电流可以用作D2受体激活的传感器。因此，这将是第一次，它将有可能测量多巴胺和谷氨酸介导的突触后电流所产生的同时释放的两个递质从多巴胺终端。这个提议的目的是确定多巴胺和谷氨酸共传递在丘脑核的功能组织。目的1将通过确定多巴胺和谷氨酸介导的突触后电流是否受到不同的调节来研究多巴胺和谷氨酸是否可以储存在不同的囊泡中。目的2将评估多巴胺和谷氨酸是否能够被储存在相同的突触囊泡的神经递质转运蛋白的活动，遗传操纵。本提案中的技术培训将包括学习记录和分析快速兴奋性突触后电流，学习执行快速扫描循环伏安法（FSCV）来测量细胞外多巴胺的浓度，学习将联合收割机FSCV与电生理学结合在一起进行同步记录，并继续发展维持转基因小鼠群体所需的技能。总的来说，这个建议将测试的假设，多巴胺和谷氨酸，而他们可能主要是隔离到不同的池的囊泡，可以释放从相同的突触囊泡在多巴胺终端在丘脑核。这将增加我们对多巴胺神经元如何能够将异质信号传递到突触后靶点的理解。

 DESCRIPTION (provided by applicant): The reinforcing properties of addictive drugs result from their effects on the mesolimbic dopamine system, which projects from the ventral tegmental area to the nucleus accumbens. Dopamine plays a central role in modulating glutamatergic inputs to medium spiny neurons, the major output neuron of the nucleus accumbens. It was recently shown that dopamine neurons release glutamate in the nucleus accumbens, in addition to their canonical release of dopamine. Since glutamate transmission in the nucleus accumbens is altered in response to chronic exposure to drugs of abuse, it is critical to understand how the release of glutamate from dopamine terminals is regulated. Previous work examining corelease used electrophysiology to measure glutamate- mediated postsynaptic currents and electrochemistry to measure the extracellular concentration of dopamine. However, it is unclear whether the extracellular dopamine measured with electrochemistry is the same pool of dopamine that drives activation of synaptic dopamine receptors. We recently described a new approach to measure synaptic dopamine transmission using overexpression of a G-protein activated inward rectifier potassium (GIRK) channel. Since endogenous D2-receptors efficiently couple to these GIRK channels, the outward potassium current can be used as a sensor of D2-receptor activation. Thus for the first time, it will be possible to measure dopamine- and glutamate-mediated postsynaptic currents resulting from simultaneous release of the two transmitters from dopamine terminals. The goal of this proposal is to determine the functional organization of dopamine and glutamate cotransmission in the nucleus accumbens. Aim 1 will examine whether dopamine and glutamate can be stored in separate pools of vesicles by determining whether dopamine- and glutamate-mediated postsynaptic currents are differentially regulated. Aim 2 will assess whether dopamine and glutamate are capable of being stored in the same synaptic vesicles by pharmacologically and genetically manipulating the activity of vesicular neurotransmitter transporters. Technical training in this proposal will inclue learning to record and analyze rapid excitatory postsynaptic currents, learning to perform fast scan cyclic voltammetry (FSCV) to measure the concentration of extracellular dopamine, learning to combine FSCV with electrophysiology in simultaneous recordings, and continuing to develop skills required to maintain a colony of transgenic mice. Overall, this proposal will test the hypothesis that dopamine and glutamate, while they may be predominantly segregated to different pools of vesicles, can be released from the same synaptic vesicles in dopamine terminals in the nucleus accumbens. This will add to our understanding of how dopamine neurons are capable of transmitting heterogeneous signals to postsynaptic targets.