ABSTRACT Background and objective: In mammals, the main biological clock that is synchronized by light is located in the suprachiasmatic nucleus of the hypothalamus, which can be divided into two distinct regions: the ventrolateral and the dorsomedial. Both behave as separate oscillators that interact with each other to form the circadian rhythm. Methods: Our objective was to develop a mathematical model to understand how these regions of the suprachiasmatic nucleus coordinate the circadian rhythm of motor activity in rats. To accomplish this, we performed simulations with light-dark cycles of 24 (T24) and 22 hours (T22) and simulations with constant darkness (CD). In the model, we developed equations to describe the circadian rhythm of a clock protein. Results: For the two light-dark and constant darkness cycles, the model was able to reproduce the synchronization with T24, the dissociation with T22, and the free-running rhythm with constant darkness. The results show that the intensity of coupling between the two oscillators and their periods define the output of the rhythm. Conclusions: The proposed model is consistent with data in the literature and suggests new experimental approaches. This model will contribute to a better understanding of the interaction between the two regions of the suprachiasmatic nucleus.
Gonçalves et al. (Mon,) studied this question.