Gu Changgui, Liang Xiaoming, Yang Huijie, Rohling Jos H T
Business School, University of Shanghai for Science and Technology, Shanghai 200093, China.
School of Physics and Electronic Engineering, Jiangsu Normal University, Xuzhou 221116, China.
Sci Rep. 2016 Feb 22;6:21412. doi: 10.1038/srep21412.
The main clock located in the suprachiasmatic nucleus (SCN) regulates circadian rhythms in mammals. The SCN is composed of approximately twenty thousand heterogeneous self-oscillating neurons, that have intrinsic periods varying from 22 h to 28 h. They are coupled through neurotransmitters and neuropeptides to form a network and output a uniform periodic rhythm. Previous studies found that the heterogeneity of the neurons leads to attenuation of the circadian rhythm with strong cellular coupling. In the present study, we investigate the heterogeneity of the neurons and of the network in the condition of constant darkness. Interestingly, we found that the heterogeneity of weakly coupled neurons enables them to oscillate and strengthen the circadian rhythm. In addition, we found that the period of the SCN network increases with the increase of the degree of heterogeneity. As the network heterogeneity does not change the dynamics of the rhythm, our study shows that the heterogeneity of the neurons is vitally important for rhythm generation in weakly coupled systems, such as the SCN, and it provides a new method to strengthen the circadian rhythm, as well as an alternative explanation for differences in free running periods between species in the absence of the daily cycle.
位于视交叉上核（SCN）的主时钟调节哺乳动物的昼夜节律。SCN由大约两万个异质性的自振荡神经元组成，其固有周期从22小时到28小时不等。它们通过神经递质和神经肽相互耦合形成一个网络，并输出统一的周期性节律。先前的研究发现，神经元的异质性会导致在强细胞耦合情况下昼夜节律的衰减。在本研究中，我们在持续黑暗的条件下研究了神经元和网络的异质性。有趣的是，我们发现弱耦合神经元的异质性使它们能够振荡并增强昼夜节律。此外，我们发现SCN网络的周期随着异质性程度的增加而增加。由于网络异质性不会改变节律的动态变化，我们的研究表明，神经元的异质性对于弱耦合系统（如SCN）中的节律产生至关重要，它提供了一种增强昼夜节律的新方法，同时也为在没有日周期的情况下物种之间自由运行周期差异提供了另一种解释。
