Dissecting functional subgroups and closed-loop circuits between the pedunculopontine nucleus and the basal ganglia

摘要 脚桥核（PPN）与基底神经节相互作用，使运动平稳，是一个神经元。 帕金森病（PD）患者深部脑刺激（DBS）的靶点。PD最常见 神经退行性运动障碍，以静止性震颤、僵硬、运动缓慢和姿势性 不稳定尾部靶向DBS刺激改善患者和啮齿动物PD模型的步态障碍 而嘴部靶向DBS在啮齿动物PD模型中使其无效。有效的PPN靶向DBS可能归因于 增加由闭环电路产生的尾侧PPN中的α振荡， PPN的活动。PPN靶向DBS在患者和啮齿动物模型中的矛盾结局 提示PPN内的功能异质性及其吻侧和尾侧亚区之间的差异。到 了解DBS如何在PPN内不同地调节运动，关键是要解剖功能性 PPN内的亚群，并确定它们如何与基底神经节沟通。在这份提案中，我 重点关注PD中选择性变性与步态相关的胆碱能PPN神经元 损伤我将使用离体全细胞膜片钳电生理学，光遗传学，钙成像， 反向珠标记（1）以表征内在电生理学特性并鉴定分子 一种区分成年小鼠头侧和尾侧胆碱能PPN神经元的标记物，（2）表征和 全面映射抑制性突触输入到PPN的区域连接，以及（3）识别 抑制性基底神经节核和PPN之间的闭环回路。初步数据显示， 两个主要的抑制性基底神经节核，黑质网状部（SNr）和苍白球 外肌（GPe），在轴突成像中差异性地投射到头侧和尾侧PPN。使用光遗传学与 全细胞膜片钳和钙成像，我们可以确认这些解剖结构的功能连接， 轴突投射和表征来自PPN上SNr和GPe的抑制电流。使用 免疫染色，我将测试五个蛋白质的差异表达选择性表达的PPN 与其他大脑区域进行比较，以确定一种分子标记， 头侧和尾侧PPN。使用光遗传学和逆转录珠标记，我将确定是否SNr-和 投射GPe的PPN神经元也从各自的基底神经节核接受抑制性输入，形成一个神经元。 闭环电路该提案将全面描述和绘制本区域的连通性， SNr和GPe的胆碱能PPN和识别闭环电路，可以帮助我们了解如何PPN 与基底神经节相互作用以调节运动，以及其变性如何成为运动缺陷的基础。 警局这些发现将指导PD中PPN回路的新药理学靶点和DBS靶向 患者

Abstract The pedunculopontine nucleus (PPN) interacts with the basal ganglia to enable smooth movement and is a target for deep brain stimulation (DBS) in Parkinson's disease (PD). PD is the most common neurodegenerative motor disorder, characterized by resting tremor, rigidity, slow movement, and postural instability. Caudal-targeted DBS stimulation improves gait impairment in both patients and rodent PD models whereas rostral-targeted DBS worsens it in rodent PD models. Effective PPN-targeted DBS may be attributed to increasing alpha oscillations in the caudal PPN generated by closed-loop circuits and increasing neuronal activity across the PPN. Contradictory outcomes of PPN-targeted DBS in both patients and rodent models suggest functional heterogeneity within the PPN and differences between its rostral and caudal subregions. To understand how DBS differentially modulates movement within the PPN, it is critical to dissect the functional subpopulations within the PPN and determine how they communicate with the basal ganglia. In this proposal, I focus on the cholinergic PPN neurons whose selective degeneration in PD also correlates with gait impairment. I will use ex vivo whole-cell patch clamp electrophysiology, optogenetics, calcium imaging, and retro bead labeling (1) to characterize the intrinsic electrophysiological properties and identify a molecular marker that differentiates rostral and caudal cholinergic PPN neurons in adult mice, (2) to characterize and comprehensively map the regional connectivity of inhibitory synaptic inputs to the PPN, and (3) to identify closed-loop circuits between the inhibitory basal ganglia nuclei and the PPN. Our preliminary data show that the two major inhibitory basal ganglia nuclei, the substantia nigra pars reticulata (SNr) and globus pallidus externus (GPe), differentially project to the rostral and caudal PPN in axon imaging. Using optogenetics with whole cell patch clamp and calcium imaging, we can confirm the functional connectivity of these anatomical axonal projections and characterize inhibitory currents from the SNr and GPe on the PPN. Using immunostaining, I will test the differential expression of five proteins selectively expressed in the PPN compared to other brain regions to identify a molecular marker that can be used as a tool to genetically access the rostral and caudal PPN. Using optogenetics and retrobead-labeling, I will determine whether SNr- and GPe-projecting PPN neurons also receive inhibitory input from the respective basal ganglia nuclei, forming a closed-loop circuit. This proposal will comprehensively characterize and map the regional connectivity of the SNr and GPe to the cholinergic PPN and identify closed-loop circuits that can help us understand how the PPN interacts with the basal ganglia to modulate movement and how its degeneration underlies motor deficits in PD. These findings will guide new pharmacological targets and DBS-targeting of the PPN circuit in PD patients.