Extrastriatal functions of dopamine

描述（由申请人提供）：越来越多的证据表明，纹状体外部位（如黑质或苍白球）的多巴胺丢失可能在帕金森综合征的发生中起重要作用。最近在动物（主要是啮齿动物）中的研究表明，多巴胺也可能在丘脑底核（subthalamic nucleus，缩写为丘脑底核）的水平上起作用。在这些动物中，已经证明了从黑质腹侧部到腹侧部的直接多巴胺能投射。此外，多巴胺神经元的活动似乎是通过多巴胺在突触前和突触后多巴胺受体上的作用来调节的，多巴胺在突触前和突触后的多巴胺受体中的消耗导致了该核中放电频率的改变和更强烈的爆发。 帕金森病状态下丘脑多巴胺能神经支配的程度和解剖结构、丘脑内多巴胺的功能以及丘脑内多巴胺丢失的影响尚未在灵长类动物中进行研究。通过这些研究，我们将在灵长类动物体内研究多巴胺供应到丘脑的解剖学和功能。在目标1下的实验中，我们将使用光镜和高分辨率电子显微镜免疫细胞化学方法的组合，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）猴脑中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在正常和帕金森病猴中局部给药对丘脑神经元活性的功能影响。我们将研究多巴胺受体激动剂和拮抗剂的影响，局部注射到视网膜微注射/记录装置。此外，还将进行微透析实验，以测量多巴胺对丘脑中GABA释放的突触前效应，以及丘脑投射主要靶点的电生理记录，即，苍白球内外段。最后，在目标3下，我们将研究正常动物中脑多巴胺受体阻断的行为效应，以及帕金森病中脑多巴胺受体的激活，期望多巴胺能传递的中断有助于帕金森病，而帕金森病状态下多巴胺能功能的替代可能改善帕金森病症状。总之，这些研究将为我们提供一个彻底的检查多巴胺能功能的灵长类动物纹状体，将帮助我们进一步了解多巴胺损失的影响，在这个纹状体外的网站，并可能确定作为一个目标的帕金森病的局部多巴胺替代策略，如基因传递方法或移植。 公共卫生相关性：丘脑底核中的神经元活动受到帕金森病中发生的基底神经节中多巴胺耗竭的强烈影响，使得该核成为功能性神经外科治疗帕金森综合征的主要目标。丘脑底核的活动变化通常被视为继发性事件，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，并产生帕金森综合征。我们将通过解剖学、电生理学、生物化学和行为学实验在帕金森病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，并可能将丘脑底核确定为目前多巴胺能治疗的一个位置。如果在丘脑底核中观察到显著的多巴胺能效应，它可能成为帕金森病患者高度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.