Johnston J D
School of Biological Sciences, University of Aberdeen, Aberdeen, UK.
J Neuroendocrinol. 2005 Jul;17(7):459-65. doi: 10.1111/j.1365-2826.2005.01326.x.
Day-length (photoperiod) is the primary environmental signal used to synchronise endogenous rhythms of physiology and behaviour. In mammals, the suprachiasmatic nuclei (SCN) of the hypothalamus house the master circadian clock. The SCN incorporate photoperiodic information and therefore measure both daily and seasonal time. Over the past decade, there have been significant advances in the understanding of the molecular basis of circadian clocks. It is now becoming apparent that the core molecular clock mechanism is itself regulated by photoperiod, although there is currently debate as to how this occurs. One recent model proposes that distinct groups of core 'clock genes' are associated with either morning or evening phases of the daily light/dark cycle. However, the validity of associating particular genes to morning and evening has been questioned. This article reviews the evidence for photoperiodic regulation of circadian clock function and then discusses alternative models that may explain the available data.
日长（光周期）是用于同步生理和行为内源性节律的主要环境信号。在哺乳动物中，下丘脑的视交叉上核（SCN）是主生物钟所在之处。SCN整合光周期信息，因此能够测量昼夜时间和季节时间。在过去十年中，人们对生物钟分子基础的理解取得了重大进展。现在越来越明显的是，核心分子时钟机制本身受光周期调节，尽管目前对于其发生方式存在争议。最近的一个模型提出，不同组的核心“时钟基因”与日常光/暗周期的早晨或傍晚阶段相关联。然而，将特定基因与早晨和傍晚相关联的有效性受到了质疑。本文回顾了生物钟功能受光周期调节的证据，然后讨论了可能解释现有数据的替代模型。
