[Internal coordination of circadian rhythms and temporal synergism in animal adaptive reactions]

The multioscillatory principle of circadian organization of organism functions is based on the ability of some organs and cells to generate independent set of oscillations with 24 hours period. Coexistence of two or more independent rhythm producers provides a flexible structure of numerous cycles that take place in organism. The stable changes of circadian rhythms can be caused either by external factors (e.g., seasonal changes of photoperiod, socially determined changes of labour regime, cycles of sleep, feeding time) or by some inner factors, e.g. stress syndrome or illness. In its turn the changes in phase relations between circadian rhythms of some hormones and neuromediators play an important role in formation of some adaptive reactions, i.e. seasonal changes in reproductive system, peculiarities of lipid metabolism, migration behaviour, preparation to hibernation, or the rate of metamorphism in amphibians. These data allow to formulate the hypothesis of temporal synergism. According to this hypothesis morphophysiological effect caused by joint action of two or more hormones or neuromediators is dependent on the phase relationships of their circadian rhythms.