Photoperiod regulates corticosterone rhythms by altered adrenal sensitivity via melatonin-independent mechanisms in Fischer 344 rats and C57BL/6J mice.
Photoperiod regulates corticosterone rhythms by altered adrenal sensitivity via melatonin-independent mechanisms in Fischer 344 rats and C57BL/6J mice.
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DOI：
10.1371/journal.pone.0039090
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发表时间：
2012
期刊：
影响因子：
3.7
通讯作者：
Yasuo S
中科院分区：
文献类型：
--
作者：
Otsuka T;Goto M;Kawai M;Togo Y;Sato K;Katoh K;Furuse M;Yasuo S
大多数生活在温带的物种通过利用光周期作为主要线索来适应环境的季节变化。光周期调节胁迫相关功能的机制还不清楚。在这项研究中，我们分析了光周期对光周期敏感的Fischer 344大鼠下丘脑-垂体-肾上腺轴的影响。我们首先研究了光周期如何影响血浆促肾上腺皮质激素（ACTH）和皮质酮浓度的昼夜变化。促肾上腺皮质激素水平没有表现出昼夜变化，在长日照和短日照条件下。短日照条件下，皮质酮水平呈现明显的节律性变化，在黑暗期达到峰值。在长日照条件下未观察到该峰值，其中未检测到显著的节律。为了分析负责皮质酮节律的光周期调节的机制，在长日照和短日照条件下维持地塞米松治疗的大鼠中，在光或暗相开始时腹腔内注射ACTH。促肾上腺皮质激素诱导更高的皮质酮水平的大鼠在黑暗中检查下短日条件下比那些保持在长日条件下。接下来，我们问褪黑激素信号是否参与皮质酮节律的光周期调节，大鼠在长日照条件下，在下午晚些时候腹腔注射褪黑激素3周。然而，褪黑激素注射并不影响皮质酮的节奏。此外，在褪黑激素缺乏的C57 BL/6 J小鼠中也观察到皮质酮节律幅度的光周期变化，其中肾上腺中的几个时钟基因和类固醇生成基因的表达谱被光周期修饰。我们的数据表明，光周期调节皮质酮的节奏通过改变肾上腺的敏感性通过褪黑激素的独立机制，可能涉及肾上腺时钟。
Most species living in temperate zones adapt their physiology and behavior to seasonal changes in the environment by using the photoperiod as a primary cue. The mechanisms underlying photoperiodic regulation of stress-related functions are not well understood. In this study, we analyzed the effects of photoperiod on the hypothalamic-pituitary-adrenal axis in photoperiod-sensitive Fischer 344 rats. We first examined how photoperiod affects diurnal variations in plasma concentrations of adrenocorticotropic hormone (ACTH) and corticosterone. ACTH levels did not exhibit diurnal variations under long- and short-day conditions. On the other hand, corticosterone levels exhibited a clear rhythm under short-day condition with a peak during dark phase. This peak was not observed under long-day condition in which a significant rhythm was not detected. To analyze the mechanisms responsible for the photoperiodic regulation of corticosterone rhythms, ACTH was intraperitoneally injected at the onset of the light or dark phase in dexamethasone-treated rats maintained under long- and short-day conditions. ACTH induced higher corticosterone levels in rats examined at dark onset under short-day condition than those maintained under long-day condition. Next, we asked whether melatonin signals are involved in photoperiodic regulation of corticosterone rhythms, and rats were intraperitoneally injected with melatonin at late afternoon under long-day condition for 3 weeks. However, melatonin injections did not affect the corticosterone rhythms. In addition, photoperiodic changes in the amplitude of corticosterone rhythms were also observed in melatonin-deficient C57BL/6J mice, in which expression profiles of several clock genes and steroidgenesis genes in adrenal gland were modified by the photoperiod. Our data suggest that photoperiod regulates corticosterone rhythms by altered adrenal sensitivity through melatonin-independent mechanisms that may involve the adrenal clock.