Regulation of Dopamine Release by ROS

描述（由申请人提供）：多巴胺（DA）是大脑中运动和情绪通路的关键调节剂。前脑结构只接受来自中脑DA神经元的DA输入，其中黑质致密部（SNc）的细胞通过黑质纹状体通路投射到背纹状体，而邻近的腹侧被盖区（VTA）的细胞通过中边缘通路投射到伏隔核和其他边缘结构。两种系统中的DA细胞具有共同的生理特性，包括体树突释放DA。然而，一个显著的区别是，黑质纹状体DA细胞在帕金森病中退化，而中脑边缘DA细胞则幸免。几种生化差异可能导致SNc更易受伤害，包括SNc中活性氧（ROS）的调节比VTA弱。这种差异可能是至关重要的，因为氧化应激被认为是帕金森氏症的一个致病因素。然而，除了具有潜在的神经毒性外，ROS还可以作为信号剂。初步数据表明过氧化氢（H202）是DA释放的调节剂。当外用时，H202抑制SNc和VTA以及背纹状体和伏隔核的释放。其他数据表明，局部刺激时产生的内源性H202抑制SNc和纹状体的DA释放，但不抑制VTA。这些数据可能揭示了黑质纹状体DA系统中一个正常的生理过程，如果H202的调节被破坏，可能会导致氧化应激。然而，目前尚不清楚H202本身是调节剂还是通过相关ROS起作用。本R21提案的目标是确定参与调节黑质纹状体和中边缘DA系统中体树突和突触DA释放的特定ROS。诱发DA释放将使用碳纤维微电极和快速扫描循环伏安法进行监测。Aim 1的实验将比较SNc和VTA中ROS对体树突DA释放的调节，Aim 2的实验将比较背纹状体和伏隔核壳的调节。令人惊讶的是，这里提出的研究将是第一个研究脆弱和抗性DA系统之间ROS调节功能差异的研究。与R21项目的目标一致，这些数据应该为黑质纹状体变性的潜在机制提供突破性的新信息。

DESCRIPTION (provided by applicant): Dopamine (DA) is a key modulator of motor and emotive pathways in the brain. Forebrain structures receive DA input exclusively from midbrain DA neurons, with cells of the substantia nigra pars compacta (SNc) projecting via the nigrostriatal pathway to dorsal striatum and those of the adjacent ventral tegmental area (VTA) project via the mesolimbic pathway to nucleus accumbens and other limbic structures. DA cells in both systems share common physiological properties, including somatodendritic release of DA. A significant difference, however, is that nigrostriatal DA cells degenerate in Parkinson's disease, whereas mesolimbic DA cells are spared. Several biochemical differences may contribute to greater SNc vulnerability, including weaker regulation of reactive oxygen species (ROS) in SNc than in VTA. This difference may be crucial, because oxidative stress has been proposed as a causal factor in Parkinson's disease. In addition to being potentially neurotoxic, however, ROS can act as signaling agents. Preliminary data implicate one ROS, hydrogen peroxide (H202), as a modulator of DA release. When applied exogenously, H202 inhibits release in the SNc and VTA as well as in dorsal striatum and nucleus accumbens. Additional data suggest that endogenous H202 generated during local stimulation inhibits DA release in the SNc and striatum, but not in the VTA. These data may reveal a normal physiological process in the nigrostriatal DA system that could contribute to oxidative stress, if regulation of H202 became disrupted. It is not clear, however, whether H202 per se is the modulator or whether it acts via related ROS. The goal of this R21 proposal is to determine specific ROS involved in modulating somatodendritic and synaptic DA release in the nigrostriatal vs. mesolimbic DA systems. Evoked DA release will be monitored using evoked using carbon-fiber microelectrodes and fast-scan cyclic voltammetry. Experiments in Aim t will compare regulation of somatodendritic DA release by ROS in the SNc and VTA, whereas those in Aim 2 will compare regulation in the dorsal striatum and the shell of the nucleus accumbens. Surprisingly, the studies proposed here would be among the first to investigate functional differences in ROS regulation between vulnerable and resistant DA systems. Consistent with the goals of the R21 program, these data should provide ground-breaking new information about underlying mechanisms in nigrostriatal degeneration.