Chronobiology Laboratory, Department of Physiology, Faculty of Biology, University of Murcia, Murcia, Spain.
Chronobiol Int. 2010 May;27(3):517-34. doi: 10.3109/07420521003743660.
Body temperature regulation within a physiological range is a critical factor for guaranteeing the survival of living organisms. The avoidance of high ambient temperatures is a behavioral mechanism used by homeothermic animals living in extreme environmental conditions. As the circadian system is involved in these thermoregulatory responses, precise phase shifts and even complete temporal niche inversion have been reported. Octodon degus, a mainly diurnal rodent from Chile, has the ability to switch its phase preference for locomotor activity to coincide with the availability of a running wheel. The aims of this work are twofold: to determine whether ambient temperature cycles, with high values during the day and low values at night (HLT(a)), can induce nocturnal chronotypes in degus previously characterized as diurnal; and to learn whether HLT(a) cycles are able to act as a zeitgeber in this dual-phase species. To this end, degus were subjected to 24 h HLT(a) cycles under both 12:12 LD and DD conditions. Two experimental groups were used, one with previous wheel running experience and another naïve group, to study the influence of the thermal cycles and previous wheel running experience on the degus' dual-phasing behavior. Temperature cycles (31.3 +/- 1.5 degrees C during the day and 24.2 +/- 1.6 degrees C at night) induced a 100% nocturnalism in previously diurnal individuals. Indeed, both entrainment with nocturnal phase angle to LD and nocturnal rhythmicity induced by masking were observed. Moreover, HLT(a) cycles acted by masking, confining wheel-running activity to the cooler phase under DD conditions, with the naïve group being more sensitive than the experienced one.
体温调节在生理范围内是保证生物生存的关键因素。避免高温环境是生活在极端环境条件下的恒温动物所采用的行为机制。由于生物钟系统参与这些体温调节反应，已经报道了精确的相位移和甚至完全的时间生态位反转。智利的一种主要在白天活动的啮齿动物——八齿鼠，有能力将其对活动的相位偏好转变为与跑步轮的可用性相吻合。这项工作的目的有两个：一是确定高温环境周期（白天高值，夜间低值）是否可以诱导先前被描述为昼行性的八齿鼠产生夜间型生物钟；二是了解高温环境周期是否能够作为这种双相物种的时间信号。为此，八齿鼠在 12:12 LD 和 DD 条件下分别接受 24 小时高温环境周期的处理。使用了两个实验组，一个是有先前跑步轮经验的组，另一个是无经验的组，以研究热周期和先前跑步轮经验对八齿鼠双相行为的影响。温度周期（白天 31.3 +/- 1.5 摄氏度，夜间 24.2 +/- 1.6 摄氏度）诱导了先前昼行性个体的 100%夜行性。事实上，观察到了与 LD 的夜间相位角的同步化以及通过掩蔽诱导的夜间节律性。此外，高温环境周期通过掩蔽作用发挥作用，将跑步轮活动限制在 DD 条件下的较冷阶段，无经验组比有经验组更敏感。
