Redlin Uwe, Mrosovsky N
Department of Animal Physiology, Biological Institute, University of Stuttgart, 70550 Stuttgart, Germany.
J Biol Rhythms. 2004 Feb;19(1):58-67. doi: 10.1177/0748730403260371.
It is known that day-active Nile grass rats, Arvicanthis niloticus, increase the amount of activity in the night relative to that in the day when provided with running wheels. This was confirmed in the present study. Animals without a wheel displayed 69.0% of their general activity in the L phase of a 12:12 h light-dark cycle; animals provided with wheels had only 48.6% of their wheel revolutions in the light. The contribution of direct (masking) responses to light to the increased nocturnality of animals with wheels was examined in two experiments. In experiment 1, masking was tested by exposing the animals to repeated cycles of 30 min of entraining light and 30 min of a different, usually dimmer light, during the L phase of a 12:12 h light-dark cycle. For animals with wheels, there was more running during the 30-min pulses of dim light or darkness than during the 30-min periods of entraining light. In contrast, for animals without wheels, there was more general activity during the 30-min periods of entraining light than during the 30-min pulses of dim light or darkness. In experiment 2, the animals were first exposed to a 12:12 h light-dark cycle and then put on a 1:10:1:12 h LDLD skeleton photoperiod. Animals with wheels increased their running during the subjective day of the skeleton photoperiod compared to that in the actual day of the 12:12 h light-dark cycle. Animals without wheels showed similar levels of general activity during the subjective day of the skeleton photoperiod and the actual day of the 12:12 h cycle. These experiments demonstrate that when Nile rats have running wheels, their increased nocturnal activity is associated with an increased suppression of locomotion in direct response to light. It is possible that changes in masking responses to light may be an essential and integral component of switching between diurnal and nocturnal activity profiles.
已知日行性的尼罗河草鼠（Arvicanthis niloticus）在配备跑步轮时，夜间活动量相对于白天会增加。本研究证实了这一点。没有轮子的动物在12:12小时明暗循环的光照阶段（L期）展现出其总体活动量的69.0%；配备轮子的动物在光照期的轮子转动次数仅占48.6%。在两个实验中研究了直接（掩盖）对光的反应对有轮子动物夜间活动增加的作用。在实验1中，通过在12:12小时明暗循环的光照阶段将动物暴露于30分钟的同步光照和30分钟不同的、通常较暗的光照的重复循环中来测试掩盖作用。对于有轮子的动物，在昏暗光照或黑暗的30分钟脉冲期间比在同步光照的30分钟期间有更多的跑步活动。相比之下，对于没有轮子的动物，在同步光照的30分钟期间比在昏暗光照或黑暗的30分钟脉冲期间有更多的总体活动。在实验2中，动物首先暴露于12:12小时明暗循环，然后置于1:10:1:12小时的LDLD骨架光周期。与在12:12小时明暗循环的实际白天相比，有轮子的动物在骨架光周期的主观白天增加了跑步活动。没有轮子的动物在骨架光周期的主观白天和12:12小时循环的实际白天展现出相似水平的总体活动。这些实验表明，当尼罗河草鼠有跑步轮时，它们夜间活动的增加与对光的直接反应中运动抑制的增加有关。对光的掩盖反应变化可能是昼夜活动模式转换的一个基本且不可或缺的组成部分。
