Neuropeptides and the Mammalian Circadian System

描述(申请人提供)：我们的长期目标是以啮齿动物视交叉上核(SCN)中的神经元为模型系统，了解环境信号调节昼夜节律振荡器的机制以及昼夜节律振荡器是如何相互耦合的。许多证据表明，谷氨酸在光信息从环境到SCN的传递中起着关键作用，PACAP肽是RHT/SCN突触连接中与谷氨酸共同传递的递质。这项应用的一个主要目标是了解PACAP在SCN神经元中调节谷氨酸诱导的信号传递的机制。我们将提供的数据表明，PACAP增强了小鼠SCN神经元的AMPA电流。此外，来自PACAP基因失活的转基因动物新品系的数据表明，光对昼夜节律系统的影响程度有所降低。因此，我们相信谷氨酸和PACAP都在调节光对昼夜节律系统的影响方面发挥了作用，尽管这一作用尚未确定。许多接受这种光信息的视黄醇受体SCN神经元本身就表达VIP和GABA。这些SCN细胞主要与其他SCN细胞突触，并推测使用这些分子向SCN中的其他细胞传递光信息。因此，第二个目标是了解VIP在SCN神经元中调节GABA诱导的信号通路的机制。在这个项目中，我们将提供与我们的假设一致的数据，即VIP作用于调节小鼠SCN神经元的GABA电流。令人鼓舞的是，来自VIP基因失活的转基因动物新品系的数据表明，昼夜节律系统发生了重大破坏，这与VIP在SCN中作为偶联剂的角色一致。通过开展这项研究，我们将解决SCN细胞如何与环境耦合以及SCN细胞如何相互耦合的重要问题。此外，我们希望利用SCN作为模型系统来更好地理解多肽共递质在介导细胞间通讯中的作用。这些问题将使用电生理和钙成像技术在小鼠脑片制备中的SCN神经元上解决。此外，缺乏PACAP和VIP的转基因小鼠将被用行为和解剖学工具进行分析。这些新开发的小鼠很可能被证明是研究昼夜节律的有用工具。

DESCRIPTION (provided by applicant): Our long-term goal is to understand the mechanisms by which environmental signals regulate circadian oscillators as well as how circadian oscillators are coupled to each other, using neurons in the rodent suprachiasmatic nucleus (SCN) as a model system. A variety of evidence suggests that glutamate plays a critical role in the transmission of photic information from the environment to the SCN and that the peptide PACAP is a co-transmitter with glutamate at the RHT/SCN synaptic connection. A major goal of this application is to understand the mechanisms by which PACAP modulates glutamate-induced signaling in SCN neurons. We will present data indicating that PACAP enhances AMPA currents in SCN neurons from mice. Furthermore, data from a new line of transgenic animals in which the PACAP gene has been inactivated demonstrate a reduction in the magnitude of the effects of light on the circadian system. Thus, we feel confident that both glutamate and PACAP play a role, be it as yet undetermined, in mediating the effects of light on the circadian system. Many of the retino-recipient SCN neurons receiving this photic information themselves express the peptide VIP as well as GABA. These SCN cells synapse largely onto other SCN cells and presumably use these molecules to communicate photic information to other cells in the SCN. Thus, a second goal is to understand the mechanisms by which VIP modulates GABA-induced signaling pathways in SCN neurons. For this project, we will present data consistent with our hypothesis that VIP acts to modulate GABA currents in SCN neurons in mice. Encouragingly, data from a new line of transgenic animals in which the VIP gene has been inactivated demonstrate major disruptions in the circadian system that are consistent with VIP's role as a coupling agent within the SCN. By carrying out this research, we will address important questions about how SCN cells are coupled to the environment as well as how SCN cells are coupled to each other. In addition, we hope to use the SCN as model system to better understand the role of peptide co-transmitters in mediating cell-to-cell communication. These questions will be addressed using electrophysiological and calcium imaging techniques on SCN neurons in a mouse brain slice preparation. In addition, transgenic mice lacking PACAP and VIP will be analyzed with behavioral and anatomical tools. These newly developed mice are likely to prove a useful tool for circadian rhythms research.