Effects of Hydrogen Peroxide on Substantia Nigra GABAergic Neuron Excitability

描述（由申请人提供）：最近的工作已经确定过氧化氢是基底节区核（包括纹状体和黑质致密部）的信号分子。目前的建议旨在研究过氧化氢作为信号分子在黑质网状部（SNr）中的功能，这在以前没有被研究过。我们将利用体外可视化的全细胞电流钳记录黑质gaba能神经元在施加外源性过氧化氢时的活性，更重要的是，通过抑制过氧化物酶来提高内源性过氧化氢水平，这将使用荧光过氧化氢敏感指示剂二氯二氢荧光素（DCF）进行验证。通过将过氧化氢水平与代谢激活的非选择性阳离子通道（即TRPM）和atp敏感钾通道（K-ATP）的药物阻滞剂相结合，将揭示过氧化氢作用的通道。Rice小组已经证明，这两种通道都是过氧化氢在其他基底核中的重要靶点。TRPM和K- ATP通道的激活将分别增加和降低SNr gaba能神经元的兴奋性。在其他实验中，将使用快速扫描循环伏安法来确定过氧化氢诱导的SNr gaba能神经元的兴奋是否有助于先前观察到的过氧化氢引起的黑质体树突多巴胺释放的抑制。过氧化氢对nmda诱导的突发放电的影响也将被研究，为过氧化氢信号在信噪比中提供额外的功能后果。信噪比的gaba能输出神经元将整个基底神经节网络的输出传递到丘脑和上丘的目标核。除了介导基底神经节在控制正常运动中的生理作用外，信噪比输出神经元的活动改变似乎也是帕金森病和其他运动障碍的许多病理生理特征的基础。阐明调节神经gaba能输出神经元兴奋性的关键因素是理解这些神经元在正常和病理条件下的生理特性的重要前提，并最终导致发现新的运动障碍治疗靶点。具体来说，过氧化氢可能有助于帕金森病中SNr神经元兴奋性的增加，其潜在机制和后果将在这里进行研究。

DESCRIPTION (provided by applicant): Recent work has established hydrogen peroxide as a signaling molecule in basal ganglia nuclei including the striatum and the substantia nigra pars compacta. The current proposal seeks to examine the functions of hydrogen peroxide as a signaling molecule in the substantia nigra pars reticulata (SNr) which has not been examined previously. In vitro visualized whole cell current clamp recordings of nigral GABAergic neurons will be used to record their activity while applying exogenous hydrogen peroxide, and more importantly, while enhancing endogenous hydrogen peroxide levels by inhibiting peroxidase enzymes, which will be verified using the fluorescent hydrogen peroxide-sensitive indicator, dichlorodihydrofluorescein (DCF). The channels underlying hydrogen peroxide's effects will be uncovered by combining manipulations of hydrogen peroxide levels with pharmacological blockers of metabolically activated nonselective cation channels (namely TRPM) and ATP-sensitive potassium channels (K-ATP), both of which have been shown by the Rice group to be important targets for hydrogen peroxide in other basal ganglia nuclei. The activation of TRPM and K- ATP channels would be expected to increase and decrease the excitability of SNr GABAergic neurons respectively. In other experiments, fast-scan cyclic voltammetry will be used to determine whether hydrogen peroxide-induced excitation of SNr GABAergic neurons contributes to the previously observed suppression of somatodendritic dopamine release in the substantia nigra caused by hydrogen peroxide. The effects of hydrogen peroxide on NMDA-induced burst firing will also be studied, providing an additional functional consequence for hydrogen peroxide signaling in the SNr. The GABAergic output neurons of the SNr convey the output of the entire basal ganglia network to target nuclei in the thalamus and superior colliculus. In addition to mediating the physiological role of the basal ganglia in the control of normal movement, it is altered activity of SNr output neurons which also seems to underlie many of the pathophysiological features of Parkinson's disease and other movement disorders. Elucidating key factors that modulate the excitability of nigral GABAergic output neurons is an important prerequisite to understanding the physiological properties of these neurons under both normal and pathological conditions and ultimately lead to discovery of novel therapeutic targets for movement disorders. Specifically, hydrogen peroxide might contribute to increases in the excitability of SNr neurons in Parkinson's disease, the potential mechanisms and consequences of which will be studied here.