Synaptic integration and intrinsic firing properties of basal ganglia neurons

基底节神经元的突触整合和内在放电特性

• 批准号: 9358605
• 负责人: ZAYD M KHALIQ
• 金额: $ 152.94万
• 依托单位: NATIONAL INSTITUTE OF NEUROLOGICAL DISORDERS AND STROKE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/9358605
• 关键词: Action Potentials; Aversive Stimulus; Basal Ganglia; Behavior; Binding Proteins; Biochemical Markers; Calcium; Calcium Signaling; Cell Death; Cells; Characteristics; Collaborations; Computer Simulation; Corpus striatum structure; DLG4 gene; Dendrites; Dendritic Spines; Dopamine; Dorsal; Frequencies; Future; Glutamates; Goals; Heterogeneity; Image; Injection of therapeutic agent; Journals; Kinetics; Laboratories; Laser Scanning Microscopy; Manuscripts; Midbrain structure; Motivation; Movement; Mus; Neck; Neurons; Neurosciences; Nucleus Accumbens; Pacemakers; Parkinson Disease; Parkinsonian Disorders; Pattern; Phase; Physiology; Play; Potassium; Potassium Channel; Property; Publications; Publishing; Recruitment Activity; Rewards; Signal Transduction; Substantia nigra structure; Synapses; Synaptic Transmission; Synaptic plasticity; Techniques; Testing; Transgenic Animals; Vertebral column; Work; bean; calbindin; dopaminergic neuron; glucosylceramidase; interest; medical schools; motor learning; neuronal cell body; novel; optogenetics; patch clamp; response; two-photon; voltage

The work in our laboratory focuses on cellular and subcellular principles of integration and excitability in dopamine-releasing neurons located in the midbrain. In a recent project, we examined the properties of spine synapses located on the dendrites of dopamine neurons, and compared the relative contribution of spine and shaft synapses to excitability. Prior to this study, evidence for the presence of dendritic spines had been mixed and there had been no functional study examining electrical and Ca2+ signaling in dendritic spines of midbrain dopamine neurons. Using two-photon uncaging of glutamate with imaging in a mouse line that expresses fluorescently tagged-PSD95 to locate glutamatergic synapses, we found that dopamine neurons express functional spines and that the size of synaptic EPSPs correlated positively with the presence of PSD-95. Lastly, we found that the characteristic slow pacemaker firing of dopamine neurons combines with boosting of spine potentials due to the narrow spine neck to produce a novel enhancement of spine Ca2+ that occurs periodically in a window from the middle to the late phase of the spike cycle. The results of this study were published in Elife in 2015. Future work will test the ionic mechanism of this pacemaker-evoked Ca enhancement and explore its implications for synaptic plasticity. Other major interests of the lab include 1) identifying functionally and biochemically unique subpopulations of midbrain dopamine neurons and 2) understanding how these neurons fit into the basal ganglia circuit. To this end, one project compared the responses to evoked and synaptically-generated GABAergic inhibition of dopamine neurons subpopulations projecting to nucleus accumbens and dorsal striatum. Midbrain dopamine neurons pause their firing in response to reward omission or aversive stimuli. Our results show that pauses in dopamine neuron firing, evoked either by stimulation of GABAergic inputs or by hyperpolarizing current injections mimicking inhibition, were enhanced by a subclass of potassium conductances recruited at voltages below spike threshold. Importantly, these A-type potassium currents recorded in mesoaccumbal neurons displayed substantially slower inactivation kinetics which, combined with weaker expression of a second conductance, hyperpolarization-activated conductance or Ih, lengthened hyperpolarization-induced delays in spiking relative to nigrostriatal neurons. Given recent anatomical studies that find that dopamine neuron subpopulations share largely overlapping inputs, these results suggest that integration of these inputs differs among dopamine neurons favoring higher sensitivity to inhibition in mesoaccumbal relative to nigrostriatal neurons, a feature that may be important for aversive signaling. A second project examined functional heterogeneity of dopamine neurons within the substantia nigra. It is known that within the SNc, which is susceptible to cell death in Parkinsons Disease, there are distinct subpopulations of vulnerable and resilient neurons that can be distinguished according to their expression of the calcium (Ca2+) binding protein, calbindin. We found that that vulnerable calbindin-lacking neurons and resilient calbindin-positive dopaminergic neurons differ substantially in their physiology, calcium signaling, dendritic branching, and excitatory synaptic transmission. Interestingly, we found that calbindin-lacking neurons display low-threshold depolarizations that were accompanied by a large increase in dendritic calcium. We found that this Ca2+enters through a subclass of voltage-gated Ca channels called T-type Ca2+ and we are currently exploring the contribution of this channel to physiology of calbindin-lacking cells. Lastly, we participated in a collaborative projects this year which resulted in two publications. One project, a collaboration with Dr. Bruce Bean at Harvard Medical School, examined the potassium channels that contribute to repolarization of action potentials in SNc dopaminergic neurons. This project was published in the Journal of Neuroscience in 2015. A second collaboration with the laboratory of Dr. Ellen Sidransky examined how glucocerebrosidase impacts parkinsonism. A manuscript of this study was recently published as an article in the Journal of Neuroscience in 2016.

我们实验室的工作主要集中在中脑多巴胺释放神经元的细胞和亚细胞整合和兴奋性原则。在最近的一个项目中，我们研究了位于多巴胺神经元树突上的棘突触的性质，并比较了棘突触和轴突触对兴奋性的相对贡献。在这项研究之前，树突棘存在的证据已经混合，并且没有功能研究检查中脑多巴胺神经元树突棘中的电和Ca 2+信号。在表达荧光标记的PSD-95的小鼠系中使用谷氨酸的双光子释放成像来定位多巴胺能突触，我们发现多巴胺神经元表达功能性棘，并且突触EPSP的大小与PSD-95的存在呈正相关。最后，我们发现，多巴胺神经元的特征性缓慢起搏器放电与由于狭窄的脊柱颈引起的脊柱电位的提高相结合，以产生一种新的脊柱Ca 2+的增强，其周期性地发生在从尖峰周期的中期到晚期的窗口中。这项研究的结果于2015年发表在Elife上。未来的工作将测试这种起搏器诱发的Ca增强的离子机制，并探索其对突触可塑性的影响。 该实验室的其他主要兴趣包括：1）识别中脑多巴胺神经元的功能和生物化学独特亚群; 2）了解这些神经元如何适应基底神经节回路。为此，一个项目比较了对投射到中脑核和背侧纹状体的多巴胺神经元亚群的诱发和突触产生的GABA能抑制的反应。中脑多巴胺神经元暂停其发射响应奖励遗漏或厌恶刺激。 我们的研究结果表明，暂停多巴胺神经元放电，诱发刺激GABA能输入或超极化电流注入模仿抑制，增强了一个子类的钾电导招募电压低于尖峰阈值。重要的是，这些A-型钾电流记录在中脑神经元表现出明显较慢的失活动力学，结合较弱的表达的第二个电导，超极化激活的电导或Ih，延长超极化诱导的延迟尖峰相对于黑质纹状体神经元。鉴于最近的解剖学研究发现，多巴胺神经元亚群共享很大程度上重叠的输入，这些结果表明，这些输入的整合多巴胺神经元之间的差异有利于更高的敏感性，抑制中脑相对于黑质纹状体神经元，一个功能，可能是重要的厌恶信号。 第二个项目研究了黑质内多巴胺神经元的功能异质性。已知在帕金森病中对细胞死亡敏感的SNc内，存在不同的脆弱和弹性神经元亚群，其可以根据其钙（Ca 2+）结合蛋白钙结合蛋白的表达来区分。我们发现，脆弱的钙结合蛋白缺乏的神经元和弹性钙结合蛋白阳性多巴胺能神经元在生理学，钙信号，树突分支，兴奋性突触传递有很大的不同。有趣的是，我们发现缺乏钙结合蛋白的神经元显示低阈值去极化，伴随着树突钙的大量增加。我们发现这种Ca 2+通过称为T型Ca 2+的电压门控Ca通道的一个亚类进入，我们目前正在探索这种通道对钙结合蛋白缺乏细胞的生理学的贡献。 最后，我们参加了今年的一个合作项目，结果出版了两本书。与哈佛医学院的布鲁斯比恩博士合作的一个项目，检查了有助于SNc多巴胺能神经元动作电位复极的钾通道。该项目于2015年发表在Journal of Neuroscience上。与Ellen Sidransky博士实验室的第二次合作研究了葡萄糖脑苷脂酶如何影响帕金森症。这项研究的手稿最近作为一篇文章发表在2016年的《神经科学杂志》上。