Extrastriatal functions of dopamine

描述(由申请人提供)：有越来越多的证据表明，纹状体以外的位置，如黑质或苍白球的多巴胺丢失可能在帕金森氏症的发展中发挥重要作用。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)水平起作用。在这些动物中，已经证实了从黑质致密部到STN的直接多巴胺能投射。此外，STN神经元的活动似乎是通过多巴胺在STN突触前和突触后的多巴胺受体上的作用来调节的，并且STN中的多巴胺耗竭导致该核的放电率改变和更强烈的爆发。帕金森病状态下，多巴胺能神经支配的范围和解剖，多巴胺在STN内的功能(S)，以及多巴胺在STN内丢失的影响，尚未在灵长类动物中得到探索。通过拟议的研究，我们将检查在灵长类动物体内向STN供应多巴胺的解剖学和功能。通过目标1下的实验，我们将结合光镜和高分辨电子显微镜免疫细胞化学方法，分析多巴胺能神经支配的程度，并表征正常和MPTP治疗(帕金森病)猴STN中多巴胺受体的亚细胞定位。目标2下的实验将研究在STN局部给予多巴胺能化合物对正常和帕金森病猴子STN神经元活动的功能影响。我们将用微量注射/记录装置将多巴胺受体激动剂和拮抗剂局部注射到STN中，以检验它们的效果。此外，还将进行微透析实验，以测量多巴胺对STN内GABA释放的突触前影响，以及STN投射的主要目标，即苍白球外部和内部节段的电生理记录。最后，在目标3下，我们将研究正常动物STN中多巴胺受体阻断的行为效应，以及帕金森病患者STN中多巴胺受体的激活，期望多巴胺能传递的中断有助于帕金森病，帕金森病状态下的多巴胺能功能的替代可能改善帕金森病的症状。综上所述，这些研究将为我们提供对灵长类STN多巴胺能功能的全面研究，有助于我们进一步了解纹状体外部位多巴胺丢失的影响，并可能确定STN是帕金森病局部多巴胺替代策略的靶点，如基因输送方法或移植。 公共卫生相关性：帕金森氏症患者基底神经节多巴胺耗竭强烈影响丘脑底核的神经元活动，使该核团成为治疗帕金森氏症的功能神经外科手术的主要靶点。丘脑底核的活动变化通常被视为次要事件，由纹状体多巴胺丢失引发。然而，越来越多的证据表明，丘脑底核内的多巴胺丢失也有助于神经元活动的变化，并导致帕金森氏症的发生。我们将通过解剖学、电生理学、生化和行为实验在帕金森灵长类动物中探索这一假说。这些研究将扩大我们对帕金森病的病理生理学的了解，并可能确定丘脑底核是当前多巴胺能治疗有效的部位。如果在丘脑底核看到显著的多巴胺能效应，它可能成为帕金森病患者高特异性局部多巴胺替代疗法的新靶点。

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.