Abstract
Circadian timing is structured in such a way as to receive information from the external and internal environments, and its function is the timing organization of the physiological and behavioral processes in a circadian pattern. In mammals, the circadian timing system consists of a group of structures, which includes the suprachiasmatic nucleus (SCN), the intergeniculate leaflet and the pineal gland. Neuron groups working as a biological pacemaker are found in the SCN, forming a biological master clock. We present here a simple model for the circadian timing system of mammals, which is able to reproduce two fundamental characteristics of biological rhythms: the endogenous generation of pulses and synchronization with the light-dark cycle. In this model, the biological pacemaker of the SCN was modeled as a set of 1000 homogeneously distributed coupled oscillators with long-range coupling forming a spherical lattice. The characteristics of the oscillator set were defined taking into account the Kuramoto's oscillator dynamics, but we used a new method for estimating the equilibrium order parameter. Simultaneous activities of the excitatory and inhibitory synapses on the elements of the circadian timing circuit at each instant were modeled by specific equations for synaptic events. All simulation programs were written in Fortran 77, compiled and run on PC DOS computers. Our model exhibited responses in agreement with physiological patterns. The values of output frequency of the oscillator system (maximal value of 3.9 Hz) were of the order of magnitude of the firing frequencies recorded in suprachiasmatic neurons of rodents in vivo and in vitro (from 1.8 to 5.4 Hz).
Highlights
Over the last few years, behaviors with periodic oscillations in biological processes have attracted the interest of many areas of science [1] and it has been demonstrated that light has non-visual systemic effects in healthy humans [2]
Periodic oscillations ranging from 20 to 28 h are called circadian rhythms and are generated by a circadian timing system (CTS), which is organized in such a way as to receive information from the external environment and the internal one
We present here a simple model for the CTS using a set of 1000 coupled oscillators homogeneously distributed as a spherical lattice with long-range coupling to represent the biological pacemaker of suprachiasmatic nucleus (SCN)
Summary
Over the last few years, behaviors with periodic oscillations in biological processes have attracted the interest of many areas of science [1] and it has been demonstrated that light has non-visual systemic effects in healthy humans [2]. Periodic oscillations ranging from 20 to 28 h are called circadian rhythms and are generated by a circadian timing system (CTS), which is organized in such a way as to receive information from the external environment (mainly from the light-dark cycle) and the internal one (associated with the physiological reactions occurring in the organism).
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More From: Brazilian Journal of Medical and Biological Research
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