Nakamura Wataru
Osaka University Graduate School of Dentistry, Japan.
Brain Nerve. 2012 Jun;64(6):647-56.
The circadian clock is crucial for efficient physiological function and drives the temporal regulation of the sleep-wake state, metabolism, and behavior. The timing of food intake and the accompanying behavior are both controlled by the internal clock, which is located in the suprachiasmatic nucleus (SCN) of the anterior hypothalamus. The SCN is considered as the master clock because the circadian rhythms for most physiological and behavioral processes are terminated after SCN ablation. The molecular framework of circadian oscillations can be best studied in the SCN. A "core" set of circadian clock genes form autoregulatory transcription-translation feedback loops that are believed to drive daily rhythms in individual cells. These clock genes are expressed in a circadian manner not only in the SCN but also in other parts of the brain and many peripheral tissues. Mammals can anticipate a predictable daily mealtime through entrainment of circadian oscillators. Because the restriction of food availability to a specific time of the day elicits anticipatory behavior even after ablation of the SCN, such behaviour is assumed to be controlled by another circadian oscillator. In this paper, we have (1) reviewed studies involving the identification of the circadian clock and (2) aimed to elucidate the complex mechanism underlying feeding-associated rhythms by achieving a deep understanding of the circadian phenotypes of the SCN.
昼夜节律时钟对高效的生理功能至关重要，并驱动睡眠-觉醒状态、新陈代谢和行为的时间调节。食物摄入的时间和伴随的行为均受位于下丘脑前部视交叉上核（SCN）的内部时钟控制。SCN被视为主时钟，因为大多数生理和行为过程的昼夜节律在SCN切除后会终止。昼夜节律振荡的分子框架可以在SCN中得到最好的研究。一组“核心”昼夜节律时钟基因形成自动调节转录-翻译反馈环，据信这些反馈环驱动单个细胞的每日节律。这些时钟基因不仅在SCN中以昼夜节律的方式表达，而且在大脑的其他部位和许多外周组织中也如此。哺乳动物可以通过昼夜节律振荡器的同步化来预测可预测的每日进餐时间。由于即使在SCN切除后，将食物供应限制在一天中的特定时间也会引发预期行为，因此这种行为被认为是由另一个昼夜节律振荡器控制的。在本文中，我们（1）回顾了涉及昼夜节律时钟鉴定的研究，（2）旨在通过深入了解SCN的昼夜节律表型来阐明与进食相关节律的复杂机制。
