Cellular Electrophysiology of the Suprachiasmatic Nuclei

描述（由申请人提供）：已知昼夜节律紊乱会导致多种疾病并损害精神和身体表现。在个体视交叉上核（SCN）神经元内，昼夜节律是由由基因转录反馈回路组成的分子钟产生的。然而，并不是所有的SCN神经元都有节律时钟基因表达，这一发现提出了一个问题，即有时钟的神经元如何相互交流，以及那些没有时钟的神经元如何产生昼夜节律输出。这种知识的缺乏是理解细胞时钟如何控制昼夜节律行为的主要障碍。在哺乳动物中，这些节律性和非节律性神经元被组织到SCN的解剖室中，SCN是主要的昼夜节律振荡器。这些隔室在时钟基因表达模式以及传出和传入神经元连接方面有所不同。我们研究的长期目标是表征SCN区室及其功能意义。我们目前的目标是确定在特定的SCN隔室中表型鉴定的神经元的突触信号传导机制，calbindin亚核（CBsn），已知其对产生昼夜运动行为很重要。我们的假设是，昼夜节律输出的产生取决于SCN隔室内部和之间的微电路。为了验证这一点，我们将使用电生理记录和免疫组织化学染色技术的独特组合来表征CBsn中的突触传递。因为我们正在使用一个确定的细胞群和一种新的技术组合，我们希望能够得出关于CBsn微电路的强有力的结论。本研究的具体目的是：1)确定CBsn神经元对视神经刺激反应的昼夜节律依赖性。2)表征血管活性肠肽（VIP）和垂体腺苷环化酶激活多肽（PACAP）对动作电位放电和突触传递的调控。3)观察CBsn神经元对转化生长因子α (TGFalpha)的反应。4)确定胃泌素释放肽（GRP）或VIP免疫反应神经元是否以昼夜节律方式激发动作电位。这些研究的完成将使我们更好地理解昼夜节律的细胞基础，并有可能更好地治疗睡眠障碍和其他昼夜节律紊乱。

DESCRIPTION (provided by applicant): Disturbances in circadian rhythms are known to contribute to a variety of diseases and to impair mental and physical performance. Within individual suprachiasmatic nucleus (SCN) neurons, circadian rhythms are generated by molecular clocks consisting of gene transcription feedback loops. Yet not all SCN neurons have rhythmic clock gene expression, a finding that raises the question of how neurons with clocks communicate with each other and with those neurons lacking clocks to generate circadian output. This lack of knowledge is a major impediment to understanding how cellular clocks govern circadian behavior. In mammals, these rhythmic and non-rhythmic neurons are organized into anatomical compartments in the SCN, which is the master circadian oscillator. These compartments differ in clock gene expression patterns, as well as in efferent and afferent neuronal connections. The long-term goal of our research is to characterize SCN compartments and their functional significance. Our current goal is to determine the synaptic signaling mechanisms of phenotypically identified neurons in a defined SCN compartment, the calbindin sub-nucleus (CBsn), which is known to be important for generating circadian locomotor behavior. Our hypothesis is that the generation of circadian outputs depends on the micro-circuitry within and between SCN compartments. To test this, we will use a unique combination of electrophysiological recording and immunohistochemical staining techniques to characterize synaptic transmission in the CBsn. Because we are using a defined cell population and a novel combination of techniques, we expect to be able to draw strong conclusions about the micro-circuitry of the CBsn. The specific aims of the proposal are: 1) Determine the circadian phase dependence of responses of CBsn neurons to optic nerve stimulation. 2) Characterize the regulation of action potential firing and synaptic transmission by vasoactive intestinal peptide (VIP) and pituitary adenyl cyclase activating polypeptide (PACAP). 3) Examine the responses of CBsn neurons to Transforming Growth Factor alpha (TGFalpha). 4) Determine whether gastrin releasing peptide (GRP) or VIP immunoreactive neurons fire action potentials in a circadian manner. Completion of these studies will lead to a better understanding of the cellular basis of circadian rhythms as well as the potential to better treat sleep disorders and other disturbances in the circadian clock.