Kas M J, Edgar D M
Sleep and Circadian Neurobiology Laboratory, Sleep Research Center, Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, California 94305, USA.
J Neurosci. 1999 Jan 1;19(1):328-33. doi: 10.1523/JNEUROSCI.19-01-00328.1999.
Mechanisms differentiating diurnal from nocturnal species are thought to be innate components of the circadian timekeeping system and may be located downstream from the circadian pacemaker within the suprachiasmatic nucleus (SCN) of the hypothalamus. In the present study, we found that the dominant phase of behavioral activity and body temperature (Tb) is susceptible to modification by a specific modality of behavioral activity (wheel-running activity) in Octodon degus, a mammal that exhibits multiple chronotypes. Seven Octodon degus exhibited diurnal Tb and locomotor activity (LMA) circadian rhythms while entrained to a 24 h light/dark cycle (LD 12:12). When the diurnal animals were provided unrestricted access to a running wheel, the overt daily rhythms in these animals inverted to nocturnal. This nocturnal pattern was sustained in constant darkness and returned to diurnal after removal of the running wheel. Six additional animals exhibited nocturnal chronotypes in LD 12:12 regardless of access to running wheels. Wheel-running activity inverted the phase preference in the diurnal animals without changing the 24 hr mean LMA or Tb levels. Because wheel running did not increase the amplitude of the pre-existing diurnal pattern, simple masking effects on LMA and Tb cannot explain the rhythm inversion. The diurnal-nocturnal inversion occurred without reversing crepuscular-timed episodes of activity, suggesting that diurnal or nocturnal phase preference is controlled separately from the intrinsic timing mechanisms within the SCN and can be dependent on behavioral or environmental factors.
区分昼行性和夜行性物种的机制被认为是昼夜节律计时系统的固有组成部分，可能位于下丘脑视交叉上核（SCN）内昼夜节律起搏器的下游。在本研究中，我们发现行为活动和体温（Tb）的主导相位易受行为活动的特定形式（轮转活动）的影响，在八齿鼠（Octodon degus）这种具有多种昼夜节律类型的哺乳动物中。七只八齿鼠在被置于24小时光照/黑暗周期（LD 12:12）时表现出昼夜体温和运动活动（LMA）昼夜节律。当给这些昼行性动物无限制地使用转轮时，这些动物明显的日常节律转变为夜行性。这种夜行性模式在持续黑暗中持续存在，在移除转轮后又恢复为昼行性。另外六只动物在LD 12:12中表现出夜行性昼夜节律类型，无论是否有转轮。轮转活动改变了昼行性动物的相位偏好，而没有改变24小时平均LMA或Tb水平。因为轮转并没有增加先前存在的昼行性模式的幅度，所以对LMA和Tb的简单掩盖效应不能解释节律反转。昼夜反转在不逆转黄昏定时活动发作的情况下发生，这表明昼夜相位偏好是与SCN内的内在计时机制分开控制的，并且可能取决于行为或环境因素。
