Gates and oscillators II: Zeitgebers and the network model of the brain clock
Gates and oscillators II: Zeitgebers and the network model of the brain clock
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DOI：
10.1177/0748730406296319
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发表时间：
2007-02-01
影响因子：
3.5
通讯作者：
Silver, Rae
中科院分区：
文献类型：
--
作者：
Antle, Michael C.;Foley, Nicholas C.;Silver, Rae
生理和行为的昼夜节律由SCN调节。当通过时钟基因的表达进行评估时，SCN内至少有2种不同的功能细胞类型是可辨别的：非节律性的、光诱导的视网膜受体细胞和不直接视网膜受体的节律性自主振荡细胞。为了预测昼夜节律系统的反应，作者提出了一个基于这些生物学特性的模型。在这个模型中，节律振荡器细胞的输出调节门细胞的活动。门单元提供维持振荡器单元之间的相位相干性的日常组织信号。在没有外部刺激的情况下，这种安排产生了一个多组分系统，能够产生自我维持的一致性节律。这项后续研究考虑了当门细胞被外部刺激激活时，系统如何响应，模拟对夹带（或相位设置）信号的响应。在这个模型中，作者发现系统可以被带入昼夜节律范围内的周期，自由运行的系统可以通过门的定时激活而相移，并且激活的相位响应曲线与动物暴露于光脉冲时观察到的相似。最后，外源性触发的门在数天内可以组织一个mammic系统，模拟光依赖再现的节奏在人口的混乱，独立的振荡器。该模型表明，单一机制（即，门细胞的输出）不仅可以解释自由运行和夹带的节律性，而且可以解释其他昼夜节律现象，包括夹带的限制、具有延迟区和提前区的PRC、以及在哺乳动物中节律性的光依赖性再现。
Circadian rhythms in physiology and behavior are regulated by the SCN. When assessed by expression of clock genes, at least 2 distinct functional cell types are discernible within the SCN: nonrhythmic, light-inducible, retinorecipient cells and rhythmic autonomous oscillator cells that are not directly retinorecipient. To predict the responses of the circadian system, the authors have proposed a model based on these biological properties. In this model, output of rhythmic oscillator cells regulates the activity of the gate cells. The gate cells provide a daily organizing signal that maintains phase coherence among the oscillator cells. In the absence of external stimuli, this arrangement yields a multicomponent system capable of producing a self-sustained consensus rhythm. This follow-up study considers how the system responds when the gate cells are activated by an external stimulus, simulating a response to an entraining (or phase-setting) signal. In this model, the authors find that the system can be entrained to periods within the circadian range, that the free-running system can be phase shifted by timed activation of the gate, and that the phase response curve for activation is similar to that observed when animals are exposed to a light pulse. Finally, exogenous triggering of the gate over a number of days can organize an arrhythmic system, simulating the light-dependent reappearance of rhythmicity in a population of disorganized, independent oscillators. The model demonstrates that a single mechanism (i.e., the output of gate cells) can account for not only free-running and entrained rhythmicity but also other circadian phenomena, including limits of entrainment, a PRC with both delay and advance zones, and the light-dependent reappearance of rhythmicity in an arrhythmic animal.