Department of Physiology, Faculty of Biology, University of Murcia, Murcia, Spain.
Chronobiol Int. 2010 Sep;27(8):1580-95. doi: 10.3109/07420528.2010.510228.
Octodon degus is a primarily diurnal rodent that presents great variation in its circadian chronotypes due to the interaction between two phase angles of entrainment, diurnal and nocturnal, and the graded masking effects of environmental light and temperature. The aim of this study was to test whether the circadian system of this diurnal rodent can be internally dissociated by imposing cycles shorter and longer than 24 h, and to determine the influence of degus chronotypes and wheel-running availability on such dissociation. To this end, wheel-running activity and body temperature rhythms were studied in degus subjected to symmetrical light-dark (LD) cycles of T28h and T21h. The results show that both T-cycles dissociate the degus circadian system in two different components: one light-dependent component (LDC) that is influenced by the presence of light, and a second non-light-dependent component (NLDC) that free-runs with a period different from the external lighting cycle. The LDC was more evident in the nocturnal than diurnal chronotype, and also when wheel running was available. Our results show that, in addition to rats and mice, degus must be added to the list of species that show an internal dissociation in their circadian rhythms when exposed to forced desynchronization protocols. The existence of a multioscillatory circadian system having two groups of oscillators with low coupling strength may explain the flexibility of degus chronotypes.
毛丝鼠是一种主要在白天活动的啮齿动物，由于两个授时相位角（即昼相与夜间相）的相互作用，以及环境光照和温度的渐增掩蔽效应，其昼夜节律时型表现出很大的变异性。本研究旨在测试这种昼行性啮齿动物的昼夜节律系统是否可以通过施加长于或短于 24 小时的周期来进行内在分离，并确定毛丝鼠昼夜节律时型和轮子活动的可利用性对这种分离的影响。为此，研究了在接受 T28h 和 T21h 对称光暗（LD）周期的毛丝鼠中轮子活动和体温节律。结果表明，这两种 T 周期将毛丝鼠的昼夜节律系统分离成两个不同的成分：一个依赖于光照的光依赖性成分（LDC），和一个自由运行的非光依赖性成分（NLDC），其周期与外部光照周期不同。LDC 在夜间型时型中比在昼间型时型中更为明显，并且在轮子活动可用时也是如此。我们的结果表明，除了大鼠和小鼠之外，毛丝鼠必须被添加到那些在暴露于强制去同步化方案时表现出内在分离的昼夜节律的物种列表中。具有两个振荡器组的多振荡器昼夜节律系统的存在，其耦合强度较低，可能解释了毛丝鼠时型的灵活性。
