Mumm B, Kaul R, Heldmaier G, Schmidt I
W.G. Kerchoff-Institut, Max-Planck-Institut für physiologische und klinische Forschung, Bad Nauheim, Federal Republic of Germany.
J Comp Physiol B. 1989;159(5):569-75. doi: 10.1007/BF00694381.
Experiments were designed to test whether or not the 24-h core temperature fluctuations in week-old rat pups are of endogenous origin. Lean (Fa/-) Zucker rat pups born on the same day to mothers maintained in two different colonies with light/dark cycles 12 h out of phase with each other were mother-reared through the first 3-4 days of life and then artificially reared simultaneously in constant dim light. Continuous, automatic measurement of core temperature and oxygen consumption during artificial rearing showed clear 24-h rhythms in 5- to 8-day-old pups. Each rhythm reached a daily minimum at a time corresponding to the beginning of the light period in the colony of origin. The amplitude of these rhythms did not diminish during artificial rearing, nor did the phase difference between the rhythms of pups originating in the two colonies systematically change. The persistent 12-h phase differences between these two groups of pups prove that the observed rhythms are not caused by exogenous stimuli. We conclude that the rat pup possesses an endogenous time-keeping mechanism that permits the expression of overt rhythmicity at the age of 1 week.
实验旨在测试一周龄幼鼠的24小时核心体温波动是否源于内源性。同一天出生的瘦型（Fa/-） Zucker幼鼠，其母亲饲养在两个不同的鼠群中，这两个鼠群的明暗周期相差12小时，幼鼠在出生后的头3 - 4天由母亲抚养，然后在持续昏暗的灯光下同时进行人工饲养。在人工饲养期间对核心体温和耗氧量进行连续自动测量，结果显示5至8日龄幼鼠有明显的24小时节律。每个节律在与原鼠群光照期开始相对应的时间达到每日最低值。这些节律的振幅在人工饲养期间没有减小，来自两个鼠群的幼鼠节律之间的相位差也没有系统性变化。这两组幼鼠之间持续存在的12小时相位差证明，观察到的节律不是由外源性刺激引起的。我们得出结论，幼鼠拥有一种内源性计时机制，该机制允许在1周龄时表现出明显的节律性。
