Afterhyperpolarization in dopamine neurons, H2O2 and KATP channels

描述：黑质腹侧部（SNc）的多巴胺（DA）神经元在基底神经节介导的运动功能中起着至关重要的作用。事实上，SNc DA神经元的丢失导致帕金森病的运动缺陷。然而，这些神经元在正常运动控制中的作用却知之甚少。最终了解帕金森病的潜在机制和治疗策略的发展在很大程度上取决于对DA神经元特性的理解。控制神经元放电模式的最关键机制之一是单个动作电位或动作电位爆发后的延长后超极化（AHP）。在DA神经元中，AHP有助于调节自发放电和诱发放电的频率和模式，并且部分由apamin敏感的Ca 2+激活的K+通道介导。此外，然而，一个apamin不敏感的组件介导的一个尚未确定的Ca 2+不敏感的通道。我们的前期研究表明，黑质多巴胺能神经元的膜特性和放电频率受内源性过氧化氢（H_2O_2）的调节，这种调节是通过ATP敏感性K ~+（KATP）通道实现的。在DA神经元中，由去极化电流注入引起的爆发式放电伴随着活性氧簇（如H2 O2）的产生增加以及延长的AHP。令人兴奋的是，在本申请中提出的新数据表明，H2 O2代谢酶，过氧化氢酶，和选择性KATP通道阻滞剂，格列本脲，显着降低DA神经元中的AHP的幅度和持续时间，这表明H2 O2和KATP通道的参与。因此，拟议的研究将测试这些因素在DA神经元中的AHP中的参与。我将使用膜片钳记录结合H2 O2荧光成像在豚鼠中脑切片的SNc DA神经元。电流钳模式将用于研究AHP幅度和持续时间，混合钳记录将用于评估AHP尾电流。目标1中的实验将解决DA神经元中的AHP是否具有H2 O2敏感组分的问题，并评估其对apamin的敏感性。H2 O2敏感性KATP通道在SNc DA神经元中的AHP中的参与将在目的2中评估。总的来说，该项目将提供独特的见解AHP的动态调节，从而DA神经元活动的H2 O2和KATP通道。公共卫生相关性该项目的重点是测试一个新的假设，关于调节黑质多巴胺能神经元的活动（SNc）。这些细胞在基底神经节介导的功能中起着至关重要的作用。事实上，SNc多巴胺神经元的损失导致帕金森病的运动缺陷。因此，这项研究可能会导致新的抗帕金森病药物的开发。因此，它与NINDS直接相关，NINDS支持专注于发现神经退行性疾病机制的项目。

DESCRIPTION: Dopamine (DA) neurons in the substantia nigra pars compacta (SNc) play a crucial role in basal- ganglia mediated motor function. Indeed loss of SNc DA neurons leads to the motor deficits in Parkinson's disease. However, the role of these neurons in the normal control of movement is poorly understood. Eventual understanding of mechanisms underlying Parkinson's disease and development of treatment strategies largely depends on understanding DA neuron properties. One of the most critical mechanisms that controls neuronal firing pattern is the prolonged afterhyperpolarization (AHP) that follows a single action potential or burst of action potentials. In DA neurons the AHP contributes to the regulation of the frequency and pattern of spontaneous and evoked discharges and is mediated in part by apamin-sensitive Ca2+-activated K+ channels. In addition, however, an apamin-insensitive component is mediated by an as yet unidentified Ca2+- insensitive channel. Our previous studies showed that membrane properties and firing frequency of DA neurons in the SNc are modulated by endogenous hydrogen peroxide (H2O2) and this modulation occurs via ATP-sensitive K+ (KATP) channels. In DA neurons burst-like firing induced by depolarizing current injection is accompanied by an increase in the production of reactive oxygen species, like H2O2, as well as a prolonged AHP. Excitingly, new data presented in this application shows that the H2O2-metabolyzing enzyme, catalase, and the selective KATP channel blocker, glibenclamide, significantly decrease the amplitude and duration of the AHP in DA neurons, suggesting an involvement of both H2O2 and KATP channels. Proposed studies will therefore test the involvement of these factors in the AHP in DA neurons. I will use patch-clamp recording coupled with fluorescence imaging of H2O2 in SNc DA neurons in guinea pig midbrain slices. Current-clamp mode will be used to study AHP amplitude and duration and hybrid-clamp recording to assess the AHP tail current. Experiments in Aim 1 will address the question whether the AHP in DA neurons has an H2O2- sensitive component and assess its sensitivity to apamin. The involvement of H2O2-sensitive KATP channels in the AHP in SNc DA neuron will be assessed in Aim 2. Overall, this project will provide unique insights into dynamic regulation of AHP and consequently DA neuron activity by H2O2 and KATP channels. PUBLIC HEALTH RELEVANCE This project is focused on testing a novel hypothesis concerning the regulation of the activity of dopaminergic neurons in the substantia nigra pars compacta (SNc). These cells play a crucial role in basal ganglia mediated function. Indeed loss of SNc dopamine neurons leads to motor deficits in Parkinson's disease. This study could therefore potentially lead to the development of novel antiparkinsonian drugs. Thus, it is of direct relevance to NINDS which supports projects focused on the discovery of mechanisms of neurodegenerative disorders.