Best J D, Maywood E S, Smith K L, Hastings M H
Department of Anatomy, University of Cambridge, Cambridge CB2 3DY, United Kingdom.
J Neurosci. 1999 Jan 15;19(2):828-35. doi: 10.1523/JNEUROSCI.19-02-00828.1999.
The suprachiasmatic nuclei (SCN) contain the principal circadian clock governing overt daily rhythms of physiology and behavior. The endogenous circadian cycle is entrained to the light/dark via direct glutamatergic retinal afferents to the SCN. To understand the molecular basis of entrainment, it is first necessary to define how rapidly the clock is reset by a light pulse. We used a two-pulse paradigm, in combination with cellular and behavioral analyses of SCN function, to explore the speed of resetting of the circadian oscillator in Syrian hamster and mouse. Analysis of c-fos induction and cAMP response element-binding protein phosphorylation in the retinorecipient SCN demonstrated that the SCN are able to resolve and respond to light pulses presented 1 or 2 hr apart. Analysis of the phase shifts of the circadian wheel-running activity rhythm of hamsters presented with single or double pulses demonstrated that resetting of the oscillator occurred within 2 hr. This was the case for both delaying and advancing phase shifts. Examination of delaying shifts in the mouse showed resetting within 2 hr and in addition showed that resetting is not completed within 1 hr of a light pulse. These results establish the temporal window within which to define the primary molecular mechanisms of circadian resetting in the mammal.
视交叉上核（SCN）包含主导生理和行为明显日常节律的主要昼夜节律时钟。内源性昼夜节律周期通过直接的谷氨酸能视网膜传入纤维至SCN被光/暗信号同步。为了解同步的分子基础，首先有必要确定光脉冲能多快地重置生物钟。我们采用双脉冲范式，结合SCN功能的细胞和行为分析，来探究叙利亚仓鼠和小鼠中昼夜节律振荡器的重置速度。对视交叉上核接受视网膜投射区域中c-fos诱导和环磷酸腺苷反应元件结合蛋白磷酸化的分析表明，视交叉上核能够分辨并对间隔1或2小时呈现的光脉冲做出反应。对接受单脉冲或双脉冲的仓鼠昼夜节律性轮转活动节律的相移分析表明，振荡器的重置在2小时内发生。延迟和提前相移都是如此。对小鼠延迟相移的检查显示在2小时内重置，此外还表明在光脉冲后1小时内重置未完成。这些结果确定了一个时间窗口，在此窗口内可定义哺乳动物昼夜节律重置的主要分子机制。
