title: A functional subdivision of the circadian clock is revealed by differential effects of melatonin administration.
abstract: The biological clock of the suprachiasmatic nuclei drives numerous physiological and behavioural circadian rhythms. In this study, we addressed the question as to whether different components of the clock may control separately various circadian functions. Using the rat transpineal microdialysis tool, we analysed the effect of clock perturbation by exogenous melatonin injection on two hormonal clock outputs: pineal melatonin and adrenal corticosterone secretions. As already reported, a single melatonin injection at the light/dark transition induces a marked increase in the endogenous pineal melatonin peak for the two following days. In the same animals, by contrast, the amplitude of the corticosterone rhythm was not altered following melatonin injection. These data show that the melatonin injection does not display an overall effect on the circadian clock, but rather influences a subpopulation of melatonin-sensitive neurons involved, among other functions, in the circadian control of the pineal pathway.
authors.affiliation: INCI, UMR7168/LC2 Département de Neurobiologie des Rythmes, CNRS-Université Louis Pasteur, IFR37 5, rue Blaise Pascal, 67084 Strasbourg Cedex, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Tritschler
authors.forename: Michel
authors.initials: M
authors.lastname: Saboureau
authors.forename: Paul
authors.initials: P
authors.lastname: Pévet
authors.forename: Béatrice
authors.initials: B
authors.lastname: Bothorel
mesh_terms: D000302:Adrenal Cortex / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects / Q000502:physiology*; D003345:Corticosterone / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000378:metabolism* / Q000494:pharmacology; D009434:Neural Pathways / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000378:metabolism*
chemical_list: D008550:Melatonin; D003345:Corticosterone