Circadian (~24 h) rhythms in behavior and physiological functions are under control of an endogenous circadian pacemaker in the suprachiasmatic nucleus (SCN) of the hypothalamus. The SCN directly drives some of these rhythms or serves as a coordinator of peripheral oscillators residing in other tissues and organs. Disruption of the circadian organization may contribute to disease, including stress-related disorders. Previous research indicates that the master clock in the SCN is resistant to stress, although it is unclear whether stress affects rhythmicity in other tissues, possibly mediated by glucocorticoids, released in stressful situations. In the present study, we examined the effect of uncontrollable social defeat stress and glucocorticoid hormones on the central and peripheral clocks, respectively in the SCN and liver. Transgenic PERIOD2::LUCIFERASE knock-in mice were used to assess the rhythm of the clock protein PERIOD2 (PER2) in SCN slices and liver tissue collected after 10 consecutive days of social defeat stress. The rhythmicity of PER2 expression in the SCN was not affected by stress exposure, whereas in the liver the expression showed a delayed phase in defeated compared to non-defeated control mice. In a second experiment, brain slices and liver samples were collected from transgenic mice and exposed to different doses of corticosterone. Corticosterone did not affect PER2 rhythm of the SCN samples, but caused a phase shift in PER2 expression in liver samples. This study confirms earlier findings that the SCN is resistant to stress and shows that clocks in the liver are affected by social stress, which might be due to the direct influence of glucocorticoids released from the adrenal gland.

中文翻译：

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社会压力和糖皮质激素会改变肝脏PERIOD2的节律性，但不会改变视交叉上核。

行为和生理功能的昼夜节律（〜24小时）受下丘脑上眼睑上核（SCN）内源性昼夜节律起搏器的控制。SCN直接驱动其中的某些节律，或充当其他组织和器官中的外围振荡器的协调器。昼夜节律组织的破坏可能导致疾病，包括与压力有关的疾病。先前的研究表明，SCN的主时钟对压力具有抵抗力，尽管目前尚不清楚压力是否会影响压力状态下释放的其他组织的节律性（可能由糖皮质激素介导）。在本研究中，我们研究了无法控制的社交挫败压力和糖皮质激素对中枢神经系统和肝脏中枢和外周时钟的影响。转基因PERIOD2 ：：LUCIFERASE敲入小鼠用于评估社交失败压力连续10天后收集的SCN切片和肝脏组织中时钟蛋白PERIOD2（PER2）的节律。SCN中PER2表达的节律性不受应力暴露的影响，而在肝脏中，与未击败的对照小鼠相比，在击败中该表达显示出延迟阶段。在第二个实验中，从转基因小鼠中收集脑切片和肝脏样品，并暴露于不同剂量的皮质酮中。皮质酮不会影响SCN样品的PER2节奏，但会引起肝脏样品中PER2表达的相移。这项研究证实了先前的发现，即SCN对压力具有抵抗力，并且表明肝脏中的时钟受到社交压力的影响，