Regulation of Dopamine Release by ROS

描述(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器。前脑结构只接受中脑DA神经元的DA输入，黑质致密部(SNC)的细胞通过黑质纹状体通路投射到背侧纹状体，邻近腹侧被盖区(VTA)的细胞通过中脑边缘通路投射到伏隔核和其他边缘结构。这两个系统中的DA细胞具有共同的生理特性，包括躯体树突状细胞释放DA。然而，一个显著的区别是，帕金森氏病患者黑质纹状体DA细胞退化，而中边缘DA细胞幸免于难。几个生化差异可能导致SNC更脆弱，包括SNC对ROS的调节弱于VTA。这种差异可能是至关重要的，因为氧化应激已被认为是帕金森氏症的一个原因。然而，除了具有潜在的神经毒性外，ROS还可以作为信号转移剂。初步数据表明，一种ROS，过氧化氢(H202)，是DA释放的调节剂。当外源性应用时，H202抑制SNC和VTA以及背侧纹状体和伏隔核的释放。更多的数据表明，在局部刺激过程中产生的内源性H202抑制了黑质和纹状体的DA释放，但不抑制VTA的DA释放。这些数据可能揭示了黑质纹状体DA系统中的一个正常生理过程，如果H202的调节被扰乱，可能会导致氧化应激。然而，尚不清楚H202本身是调节器还是通过相关的ROS发挥作用。本R21建议的目的是确定特定的ROS参与调节黑质纹状体与中脑边缘DA系统的躯体树突和突触DA的释放。诱发的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中的实验将比较ROS在黑质和VTA对躯体树突DA释放的调节，而Aim 2中的实验将比较背侧纹状体和伏核外壳的调节。令人惊讶的是，这里提出的研究将是第一批调查脆弱和耐药DA系统之间ROS调节功能差异的研究之一。与R21计划的目标一致，这些数据应该为黑质纹状体变性的潜在机制提供开创性的新信息。

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.