Independence of circadian entrainment state and responses to melatonin in male Siberian hamsters.
Independence of circadian entrainment state and responses to melatonin in male Siberian hamsters.
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DOI：
10.1186/1472-6793-3-10
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发表时间：
2003-10-03
期刊：
影响因子：
--
通讯作者：
Gorman MR
中科院分区：
文献类型：
--
作者：
Gorman MR
生理和行为的季节性波动取决于昼夜节律系统编程的褪黑激素分泌的持续时间。然而，给定持续时间的褪黑素信号可以引起不同的反应，这取决于动物之前是否接触到更长或更短的光周期信号(即它的光周期历史)。这份报告研究了西伯利亚雄性仓鼠的光周期历史的两个方面--先前的褪黑素暴露或昼夜节律系统的夹带状态--对于对共同的光周期信号产生或有反应至关重要。在实验1中，每天注射5h或10h的褪黑素分别刺激或抑制性腺生长，但不影响运动节律对长或短日长的夹带，从而证明褪黑素的历史和夹带状态可以在实验上分离。这些操作在实验2中重复，动物随后暴露在12周的自然褪黑激素信号中，以揭示光周期历史效应。性腺反应不同于先前的褪黑激素暴露，但不受昼夜节律夹带状态的影响。实验3证明，在暴露于长光周期的四周内，可以传授新的光周期历史。此外，在持续释放褪黑素胶囊的同时治疗的动物中，这种效应被阻断，这种胶囊掩盖了内源性褪黑素信号：在移除植入物后，性腺的反应不是依赖于紧邻之前的昼夜节律夹带状态，而是依赖于植入物之前更遥远的光周期条件。光周期信号作为先前条件的函数的解释具体取决于褪黑素暴露的历史。昼夜夹带状态的光周期调节对褪黑素信号的解释贡献最小。
Seasonal fluctuations in physiology and behavior depend on the duration of nocturnal melatonin secretion programmed by the circadian system. A melatonin signal of a given duration, however, can elicit different responses depending on whether an animal was previously exposed to longer or shorter photoperiod signals (i.e., its photoperiodic history). This report examined in male Siberian hamsters which of two aspects of photoperiod history – prior melatonin exposure or entrainment state of the circadian system – is critical for generating contingent responses to a common photoperiodic signal. In Experiment #1, daily melatonin infusions of 5 or 10 h duration stimulated or inhibited gonadal growth, respectively, but had no effect on entrainment of the locomotor activity rhythm to long or short daylengths, thereby demonstrating that melatonin history and entrainment status could be experimentally dissociated. These manipulations were repeated in Experiment #2, and animals were subsequently exposed to a 12 week regimen of naturalistic melatonin signals shown in previous experiments to reveal photoperiodic history effects. Gonadal responses differed as a function of prior melatonin exposure but were unaffected by the circadian entrainment state. Experiment #3 demonstrated that a new photoperiodic history could be imparted during four weeks of exposure to long photoperiods. This effect, moreover, was blocked in animals treated concurrently with constant release melatonin capsules that obscured the endogenous melatonin signal: Following removal of the implants, the gonadal response depended not on the immediately antecedent circadian entrainment state, but on the more remote photoperiodic conditions prior to the melatonin implant. The interpretation of photoperiodic signals as a function of prior conditions depends specifically on the history of melatonin exposure. The photoperiodic regulation of circadian entrainment state contributes minimally to the interpretation of melatonin signals.