Modeling of the suprachiasmatic nucleus based on reduced molecular clock mechanisms.

One of the physiological substrates of circadian rhythms is known to be located in the suprachiasmatic nucleus (SCN), which unilaterally contains up to 10,000 or more pacemaker cells. Specific molecular clock mechanisms are working within each cell. Here, in order to prevent complexity explosion in understanding the dynamics of SCN, the molecular clock mechanisms are modeled in a reduced form preserving their dynamical characteristics. The reduced cellular models are coupled by diffusions of activating and suppressing agents so as to construct the whole SCN model. The resulting spatial patterns of entrainment are studied under varied diffusion constants. The simulation results suggest validity of reduction of the molecular dynamics as well as usefulness of the strategy employed to model the hierarchical biological system.