CIRCADIAN-RHYTHMS - ANATOMICAL, FUNCTIONAL AND MOLECULAR-BASES

In all living organisms, circadian rhythms are the cyclic expression of biological processes according to a period close to 24h. The generation of rhythms and their synchronization to the solar cycle in mammals depend upon a central nervous structure, the suprachiasmatic nucleus, an endogenous clock reset by a retinal information. The synchronization mechanism depends on a cascade of molecular events involving various membrane receptors, immediate-early genes and late response genes. The recent discovery of se veral steps of this cascade III rodents is an outstanding example of direct link between molecular biology and integrative physiology. It has also been established during the last years that in addition to the internal clock, the regulation of neuroendocrine rhythms by light involves several brain areas targets of optic pathways that are independent from the proper visual system: they are called photic pathways. Knowing the organization of this specific system, which is basically similar in humans and other mammals, will provide a basis for the settlement of treatment of dysregulations such as jet lag, shift work or seasonal affective disorders.