Synaptic Transmission, Plasticity and Integration in the Subthalamic Nucleus

描述(申请人提供)：帕金森病(PD)患者的运动迟缓、僵直和运动迟缓的衰弱症状与GABA能苍白外球(GPE)和谷氨酸能丘脑底核(STN)以及相关的皮质-基底节-丘脑皮质网络中神经元活动的频率和模式的变化密切相关。在特发性帕金森病和实验性帕金森病中，GPE和STN分别表现为低活动和多活动，并表现为异常的同步、节律性、爆发式放电。帕金森病实验性模型黑质多巴胺神经元急性消失后，STN异常活动缓慢出现，并逐渐增强，2-3周后达到稳定峰值。这一过程表明，细胞和网络属性的适应性变化有助于帕金森病患者STN活动的发展。由于GPE可以有效地调节STN活动的频率和同步性，并能在STN中产生反弹爆发放电，因此我们用电生理、分子和解剖学方法比较了GPE-STN在对照和6-羟基多巴胺损毁的啮齿动物中的传递。这些研究表明，在失去多巴胺2-3周后，通过突触连接的增殖，GPE-STN的投射显著增强。因此，这种改变可能是帕金森病患者GPE-STN活性异常的主要原因之一。在这里，我们建议研究多巴胺丢失后GPE-STN传递改变的时间过程、性质、潜在机制和功能后果。我们建议应用细胞生理学来测量GPE-STN突触的功能和功能障碍；解剖学方法来定义GPE-STN突触可塑性的结构和分子基础；双光子激光扫描显微镜和光遗传学来定义触发突触可塑性的钙离子来源；病毒载体、分子和生化方法来确定潜在的分子机制并使我们能够操纵GPE-STN的传递。我们提出4个具体目标：目的1.确定实验性帕金森病患者GPE-STN突触传递改变的时程和性质。我们假设GPE-STN传递的改变与帕金森病患者STN活动的发展相关；目的2.确定导致实验性PD中GPE-STN突触传递增强的触发因素。我们假设STN谷氨酸受体和/或Cav通道的过度激活导致实验性帕金森病GPE-STN突触传递的增强；目的3.确定GPE-STN突触传递增强的细胞和分子机制。我们假设STN谷氨酸受体的过度激活和/或STN神经元的过度活动导致细胞内钙离子的增加，从而激活介导突触增强和增殖的信号级联反应；目的4.确定慢性多巴胺耗竭对STN神经元动作电位依赖性抑制的影响。我们假设GPE-STN神经元的自主活动不会因多巴胺耗竭而改变，GPE-STN的抑制作用通过增强GPE-STN的连接而增加。

DESCRIPTION (provided by applicant): The debilitating motor symptoms of akinesia, bradykinesia and rigidity in Parkinson's disease (PD) are intimately related to changes in the frequency and pattern of neuronal activity in the reciprocally connected GABAergic external globus pallidus (GPe) and glutamatergic subthalamic nucleus (STN) and associated cortico-basal ganglia-thalamocortical networks. In idiopathic and experimental PD the GPe and STN exhibit hypo- and hyperactivity, respectively, and abnormal synchronous, rhythmic, burst firing. Following acute loss of substantia nigra dopamine neurons in experimental models of PD abnormal STN activity emerges slowly and intensifies gradually until it reaches a stable maximum after 2-3 weeks. This process suggests that adaptive changes in cellular and network properties contribute to the development of parkinsonian STN activity. Because the GPe potently regulates the frequency and synchronization of STN activity and can generate rebound burst firing in the STN, GPe-STN transmission was compared in control and 6-hydroxydopamine-lesioned rodents using electrophysiological, molecular and anatomical approaches. These studies revealed that 2-3 weeks after loss of dopamine the GPe-STN projection had strengthened considerably through proliferation of synaptic connections. This alteration could therefore be a major contributor to the emergence of abnormal GPe-STN activity in PD. Here we propose to study the timecourse, nature, underlying mechanisms and functional consequences of alterations in GPe-STN transmission that follow the loss of dopamine. We propose to apply cellular physiology to measure GPe-STN synaptic function and dysfunction; anatomical approaches to define the structural and molecular bases of GPe-STN synaptic plasticity; 2-photon laser scanning microscopy and optogenetics to define the sources of Ca2+ that trigger synaptic plasticity; viral vector, molecular and biochemical approaches to define the underlying molecular mechanisms and enable us to manipulate GPe-STN transmission. We propose 4 Specific Aims: Aim 1. Determine the timecourse and nature of alterations in GPe-STN synaptic transmission in experimental PD. We hypothesize that alterations in GPe-STN transmission are correlated with the development of parkinsonian STN activity; Aim 2. Determine the triggers leading to potentiation of GPe-STN synaptic transmission in experimental PD. We hypothesize that hyperactivation of STN glutamate receptors and/or Cav channels leads to the potentiation of GPe-STN synaptic transmission in experimental PD; Aim 3. Determine the cellular and molecular mechanisms underlying the potentiation of GPe-STN synaptic transmission. We hypothesize that hyperactivation of STN glutamate receptors and/or hyperactivity of STN neurons leads to an increase in intracellular Ca2+, which activates signaling cascades that mediate synaptic potentiation and proliferation; Aim 4. Determine the impact of chronic dopamine depletion on action potential-dependent inhibition of STN neurons. We hypothesize that the autonomous activity of GPe-STN neurons is not altered by dopamine depletion and that GPe-STN inhibition is increased through potentiation of GPe-STN connectivity.