School of Bioengineering, Dalian University of Technology, Dalian, Liaoning 116024, China.
Advanced Institute for Medical Sciences, Dalian Medical University, Dalian, Liaoning 116044, China.
Physiol Behav. 2022 Oct 15;255:113917. doi: 10.1016/j.physbeh.2022.113917. Epub 2022 Jul 16.
The mammalian circadian system has a plasticity in a certain range, rather than a strict 24-hour cycle, with considerable variations among species, strains, and ages. As the most widely used mouse strains in circadian research, C57BL/6 and BALB/c mice were well known to have different internal periods and responses to various non-24-hour light-dark cycles. However, their entrainable range of circadian behavior was not specifically studied, neither was the effect of aging. Besides, it is not well known if mice with appeared behavioral adaptation are really healthy. In the current study, we exposed C57BL/6 and BALB/c mice at 3 months and 18 months old to a series of short (T cycles < 24 h) and long (T cycles > 24 h) light-dark cycles. Wheel running activities were monitored continuously for calculation of the entrainable range and glucose homeostasis was investigated to reflect their health status. Our results showed that the range in both young and old C57BL/6 mice is between T23 and T26. By contrast, due to the strong adaptability to extreme LD cycles, the entrainable range on a circadian scale in both young and old BALB/c mice cannot be well determined. Despite the adaptation appeared at the behavioral level, glucose homeostasis revealed by glucose tolerance test and insulin tolerance test was impaired in mice upon T cycle treatment. In summary, our study explored the entrainment range in two popular mouse strains and suggested that behavioral adaptation may not well reflect their health status.
哺乳动物的生物钟系统具有一定范围内的可塑性，而不是严格的 24 小时周期，不同物种、品系和年龄之间存在很大差异。作为昼夜节律研究中最常用的两种小鼠品系，C57BL/6 和 BALB/c 小鼠的内部周期不同，对各种非 24 小时光照-黑暗周期的反应也不同。然而，它们的生物钟行为可适应范围并没有被专门研究过，也没有研究衰老的影响。此外，行为适应的小鼠是否真的健康也不清楚。在本研究中，我们分别在 3 个月大和 18 个月大时，将 C57BL/6 和 BALB/c 小鼠暴露于一系列短（T 周期 < 24 小时）和长（T 周期 > 24 小时）光照-黑暗周期中。连续监测轮跑活动以计算可适应范围，并调查葡萄糖稳态以反映它们的健康状况。我们的结果表明，年轻和年老的 C57BL/6 小鼠的适应范围在 T23 和 T26 之间。相比之下，由于对极端 LD 周期的适应性很强，年轻和年老的 BALB/c 小鼠在昼夜尺度上的可适应范围无法很好地确定。尽管在行为层面上出现了适应，但葡萄糖耐量试验和胰岛素耐量试验所揭示的葡萄糖稳态在 T 周期处理的小鼠中受损。总之，我们的研究探讨了两种常用小鼠品系的适应范围，并表明行为适应可能不能很好地反映它们的健康状况。
