Extrastriatal functions of dopamine

描述（由申请人提供）：越来越多的证据表明，纹状体外如黑质或苍白球的多巴胺丢失可能在帕金森病的发展中起重要作用。最近对动物（主要是啮齿动物）的研究表明，多巴胺也可能在丘脑底核（STN）水平上起作用。在这些动物中，多巴胺能从黑质致密部直接投射到STN已被证实。此外，STN神经元的活动似乎是通过多巴胺在STN突触前和突触后多巴胺受体的作用来调节的，并且STN中多巴胺的消耗导致该核的放电速率改变和更强烈的破裂。在灵长类动物中，多巴胺能神经支配的范围和解剖结构、多巴胺在STN内的功能以及帕金森状态下STN中多巴胺丢失的影响尚未被探索。通过本研究，我们将在灵长类动物体内研究多巴胺向STN供应的解剖结构和功能。在aim 1下的实验中，我们将利用光镜和高分辨率电镜免疫细胞化学方法相结合的方法，分析正常和MPTP治疗（帕金森病）猴子STN中多巴胺能神经支配的程度，并表征多巴胺受体的亚细胞定位。目标2下的实验将研究多巴胺能化合物对正常和帕金森猴STN神经元活动的功能影响，这些化合物局部施用于STN。我们将检查多巴胺受体激动剂和拮抗剂的作用，通过显微注射/记录设备局部注射到STN。此外，将进行微透析实验，测量多巴胺对STN中GABA释放的突触前效应，以及STN投射的主要目标，即外、内白质节段的电生理记录。最后，在aim 3下，我们将研究正常动物STN中多巴胺受体阻断的行为影响，以及帕金森病中STN中多巴胺受体的激活，期望多巴胺能传递的破坏有助于帕金森病，而帕金森状态下多巴胺能功能的替代可能会改善帕金森症状。综上所述，这些研究将为我们提供灵长类STN中多巴胺能功能的全面研究，将帮助我们进一步了解多巴胺在这一肋外部位损失的影响，并可能确定STN作为帕金森病局灶性多巴胺替代策略的靶点，如基因传递方法或移植。

DESCRIPTION (provided by applicant): There is accumulating evidence that dopamine loss at locations outside of the striatum such as the substantia nigra or the globus pallidus may play a significant role in the development of parkinsonism. Recent studies in animals, primarily rodents) have suggested that dopamine may also act at the level of the subthalamic nucleus (STN). In these animals, a direct dopaminergic projection from the substantia nigra pars compacta to the STN has been demonstrated. Furthermore, it appears that the activity of STN neurons is modulated through actions of dopamine at pre- and post-synaptic dopamine receptors in the STN, and that dopamine depletion in the STN leads to altered firing rates and more intense bursting in this nucleus. The extent and anatomy of the dopaminergic innervation of the STN, the function(s) of dopamine within the STN, and the effects of dopamine loss in the STN in the parkinsonian state have not been explored in primates. With the proposed studies, we will examine the anatomy and function of the dopamine supply to the STN in vivo in primates. With the experiments under aim 1, we will analyze the extent of the dopaminergic innervation and characterize the subcellular localization of dopamine receptors in the STN of normal and MPTP- treated (parkinsonian) monkeys, using a combination of light-microscopic and high resolution electron microscopic immunocytochemical methods. The experiments under aim 2 will study the functional effects of dopaminergic compounds, locally administered in the STN, on the activity of STN neurons in normal and parkinsonian monkeys. We will examine the effects of dopamine receptor agonists and antagonists, injected locally into the STN with a microinjection/recording device. In addition, microdialysis experiments will be carried out to measure the presynaptic effects of dopamine on GABA release in the STN, as well as electrophysiological recordings in the primary targets of STN projections, i.e., the external and internal pallidal segments. Finally, under aim 3, we will study the behavioral effects of dopamine receptor blockade in the STN in normal animals, and activation of dopamine receptors in the STN in parkinsonism, with the expectation that disruption of dopaminergic transmission contributes to parkinsonism, and replacement of dopaminergic function in the parkinsonian state may ameliorate parkinsonian symptoms. Taken together, these studies will provide us with a thorough examination of dopaminergic functions in the primate STN, will help us to understand further the effects of dopamine loss at this extrastriatal site, and may identify the STN as a target for focal dopamine replacement strategies in parkinsonism, such as gene delivery methods or grafting. PUBLIC HEALTH RELEVANCE: The neuronal activity in the subthalamic nucleus is strongly affected by the dopamine depletion in the basal ganglia that occurs in Parkinson's disease, making this nucleus the primary targets of functional neurosurgery to treat parkinsonism. Activity changes in the subthalamic nucleus are usually seen as secondary events, triggered by striatal dopamine loss. However, there is accumulating evidence that dopamine loss within the subthalamic nucleus also contributes to the neuronal activity changes, and to the generation of parkinsonism. We will explore this hypothesis in parkinsonian primates through anatomical, electrophysiologic, biochemical and behavioral experiments. These studies will expand our knowledge of the pathophysiology of parkinsonism, and may identify the subthalamic nucleus as a location at which current dopaminergic therapies work. If significant dopaminergic effects are seen in the subthalamic nucleus, it may emerge as a new target for highly specific local dopamine replacement therapies for parkinsonian patients.