Rani Sangeeta, Singh Sudhi, Malik Shalie, Singh Jyoti, Kumar Vinod
DST-IRHPA Center for Excellence in Biological Rhythm Research, Department of Zoology, University of Lucknow, India.
Chronobiol Int. 2009 May;26(4):653-65. doi: 10.1080/07420520902926009.
This study investigates the relative strengths of food and light zeitgebers in synchronization of circadian rhythms of Indian weaver birds and the role of the pineal gland in food-induced synchronization of the circadian activity rhythms. Two experiments were performed. In the first experiment, six birds were concurrently exposed for 10 days to PA 12/12 (12 h food present: 12 h food absent) and LD 12/12 (12 h light: 12 h dark). Then, the PA 12/12 cycle was reversed: food was present during the dark period of the LD 12/12 cycle. After 15 days, birds were released into constant dim light (LL(dim)). During exposure to overlapping light and food availability periods, birds were active only during the daytime. When light and food availability periods were presented in antiphase, two of six birds became night active. However, with the removal of the light zeitgeber (i.e., under LL(dim)), all birds were synchronized with reversed PA 12/12; hence, they were active during the subjective night (i.e., the period corresponding to darkness [ZT12-0] of the preceding LD 12/12). The second experiment examined whether the pineal contributed to the food-induced synchronization. After two weeks of concurrent PA 12/12 and LD 12/12 exposure, six birds were released into LL(dim) for 2.5 weeks. Under LL(dim), five of six birds were synchronized to PA 12/12 with the circadian period (tau, tau) = 24 h. The LD 12/12 was restored, and after seven days, birds were pinealectomized (pinx). After 2.5 weeks, pinx birds were again released into LL(dim) for 2.5 weeks. Under LL(dim), pinx birds did not become arrhythmic; instead, they appeared synchronized to PA 12/12 with tau = 24 h (n = 4) or approximately 24 h (n = 2). We conclude that both food and light act as zeitgebers, although light appears to be the relatively stronger cue when the two are present together, as in the natural environment. We also found that the pineal is not necessary for food-induced synchronization. The findings suggest that food cycles could act as the synchronizer of circadian rhythmicity in biological functions in individuals held in an aperiodic environment.
本研究调查了食物和光照授时因子对印度织雀昼夜节律同步的相对强度，以及松果体在食物诱导的昼夜活动节律同步中的作用。进行了两个实验。在第一个实验中，六只鸟同时暴露于PA 12/12（12小时有食物：12小时无食物）和LD 12/12（12小时光照：12小时黑暗）环境中10天。然后，将PA 12/12周期颠倒：在LD 12/12周期的黑暗期提供食物。15天后，将鸟放入持续昏暗光照（LL(dim)）环境中。在光照和食物供应期重叠时，鸟只在白天活动。当光照和食物供应期呈反相时，六只鸟中有两只在夜间活动。然而，去除光照授时因子后（即处于LL(dim)环境下），所有鸟都与颠倒的PA 12/12同步；因此，它们在主观夜间活动（即对应于前一个LD 12/12的黑暗期[ZT12 - 0]）。第二个实验研究了松果体是否有助于食物诱导的同步。在同时暴露于PA 12/12和LD 12/12两周后，六只鸟被放入LL(dim)环境中2.5周。在LL(dim)环境下，六只鸟中有五只与PA 12/12同步，昼夜周期（tau，τ）= 24小时。恢复LD 12/12环境，七天后，对鸟进行松果体摘除（pinx）。2.5周后，松果体摘除的鸟再次被放入LL(dim)环境中2.5周。在LL(dim)环境下，松果体摘除的鸟没有变得无节律；相反，它们似乎与PA 12/12同步，tau = 24小时（n = 4）或约24小时（n = 2）。我们得出结论，食物和光照都可作为授时因子，尽管在自然环境中两者同时存在时光照似乎是相对更强的信号。我们还发现松果体对于食物诱导的同步并非必需。这些发现表明，在非周期性环境中的个体，食物周期可作为生物功能昼夜节律的同步器。
