NEURAL BASIS OF MAMMALIAN CIRCADIAN ORGANIZATION

哺乳动物下丘脑的视交叉上核（SCN）是控制许多生理过程和行为的近24小时（昼夜节律）节律系统的一部分。这个定时系统产生昼夜节律行为，将其与当地时间同步，在每种行为和日常环境周期之间设置适当的相位关系，并根据特定的环境条件（例如，季节性光周期）雕刻每种行为的持续时间和幅度。尽管单个SCN神经元极有可能产生昼夜节律周期，但尚不确定这些复杂的昼夜节律行为是在单细胞水平上产生的，还是通过SCN组织内的细胞相互作用产生的，还是通过与其他神经和/或非神经系统的相互作用产生的。此外，SCN向其他大脑区域传递时间信息的途径和机制在很大程度上仍未被探索。提出的实验将研究神经元在体内、培养组织和分散中的昼夜节律特性和细胞间通讯机制。光周期或明暗周期持续时间的变化导致经典描述的活动开始时间、活动持续时间或活动节律表达周期的变化。具体目标1将确定细胞组织的水平和机制，负责维持行为与当地时间之间适当的相位关系，再同步的动力学（例如，相移瞬态），以及通过引入刺激参数控制昼夜节律波形。具体目标2将解决在昼夜节律行为可塑性的神经起源。我们将确定周期和波形的变化是在单个SCN神经元水平上产生的，还是在SCN内产生的，还是在神经组织的其他水平上产生的。最后，具体目标3将确定在具体目标1和2中检查的一些行为的年龄相关恶化的轨迹。这些实验将得到最近新技术发展的极大帮助，这些新技术可以在体外记录细胞节律数周。我们将通过监测转基因细胞中的per1荧光素酶活性和使用多电极阵列的单个神经元的电活动来测量分子节律性。这些程序使我们能够记录从至少9个月大的动物身上提取的神经元。综上所述，这些研究将为了解不同水平的神经组织如何促进哺乳动物昼夜节律行为的产生和控制提供见解。

The suprachiasmatic nucleus (SCN) of the mammalian hypothalamus is part of a system that controls the near 24-hour (circadian) rhythms in many physiological processes and behaviors. This timing system generates circadian behaviors, synchronizes them to local time, sets an appropriate phase relationship between each behavior and daily environmental cycles, and sculpts the duration and amplitude of each behavior in response to particular environmental conditions (e.g., seasonal photoperiod). Although it is highly likely that individual SCN neurons generate circadian periodicities, it is uncertain whether these complex circadian behaviors arise at the level of single cells, through cellular interactions within the SCN tissue, or through interactions with other neural and/or non-neural systems. Furthermore, the pathways and mechanisms by which the SCN conveys timing information to other brain regions remain largely unexplored. The proposed experiments will examine the circadian properties and mechanisms of intercellular communication of neurons in vivo, and in cultured tissues and dispersals. Changes in the duration of the photoperiod or period of the light:dark cycle result in classically described changes in the time of activity onset, the duration of activity, or the expressed period of activity rhythms. Specific aim 1 will determine the level of cellular organization and mechanisms responsible for maintaining an appropriate phase relationship between the behavior and local time, the kinetics of resynchronization (e.g., phase shifting transients), and the control of circadian waveform by entraining stimulus parameters. Specific aim 2 will address the neural origins of plasticity in circadian behavior. We will determine whether changes in period and waveform are generated at the level of single SCN neurons, within the SCN or at other levels of neural organization. Finally, specific aim 3 will determine the locus of age-related deterioration of some of the behaviors examined in specific aims 1 and 2. These experiments will be aided greatly by the recent development of new technologies that enable recording of cellular rhythmicity for weeks in vitro. We will measure molecular rhythmicity by monitoring per1:luciferase activity in transgenic cells and electrical activity from individual neurons using multielectrode arrays. These procedures allow us to record from neurons taken from animals at least 9 months of age. Taken together, these studies will provide insights into how different levels of neural organization contribute to the generation and control of mammalian circadian behaviors.