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Timed hypocaloric feeding and melatonin synchronize the suprachiasmatic clockwork in rats, but with opposite timing of behavioral output

Authors

  • Ivette Caldelas,

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    • *

      Present address: Departamento de Biología Celular y Fisiología, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, 04510 México D.F., México.

    • I.C. and C.F. contributed equally to this work.

  • Celine A. Feillet,

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    • I.C. and C.F. contributed equally to this work.

  • Hugues Dardente,

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    • Present address: Douglas Hospital Research Centre, McGill University, Montreal, Quebec H4H1R3, Canada.

  • Françoise Eclancher,

    1. Laboratory of Neurobiology of Rhythms, Centre National de la Recherche (UMR7518), Departement of Neuroscience (IFR37), University Louis Pasteur, 5 rue Blaise Pascal 67084 Strasbourg cedex, France
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  • André Malan,

    1. Laboratory of Neurobiology of Rhythms, Centre National de la Recherche (UMR7518), Departement of Neuroscience (IFR37), University Louis Pasteur, 5 rue Blaise Pascal 67084 Strasbourg cedex, France
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  • Sylviane Gourmelen,

    1. Laboratory of Neurobiology of Rhythms, Centre National de la Recherche (UMR7518), Departement of Neuroscience (IFR37), University Louis Pasteur, 5 rue Blaise Pascal 67084 Strasbourg cedex, France
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  • Paul Pévet,

    1. Laboratory of Neurobiology of Rhythms, Centre National de la Recherche (UMR7518), Departement of Neuroscience (IFR37), University Louis Pasteur, 5 rue Blaise Pascal 67084 Strasbourg cedex, France
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  • Etienne Challet

    1. Laboratory of Neurobiology of Rhythms, Centre National de la Recherche (UMR7518), Departement of Neuroscience (IFR37), University Louis Pasteur, 5 rue Blaise Pascal 67084 Strasbourg cedex, France
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Dr E. Challet, as above.
E-mail: challet@neurochem.u-strasbg.fr

Abstract

Temporal organization of the molecular clockwork and behavioral output were investigated in nocturnal rats housed in constant darkness and synchronized to nonphotic cues (daily normocaloric or hypocaloric feeding and melatonin infusion) or light (light–dark cycle and daily 1-h light exposure). Clock gene (Per1, Per2 and Bmal1) and clock-controlled gene (Vasopressin) expression in the suprachiasmatic nuclei was assessed over 24 h. Light and exogenous melatonin synchronized the molecular clock, signaling, respectively, ‘daytime’ and ‘nighttime’, without affecting temporal organization of behavioral output (rest/activity rhythm). By contrast, synchronization to hypocaloric feeding led to a striking temporal change between gene expression in the suprachiasmatic clock and waveform of locomotor activity rhythm, rats then becoming active during the subjective day (diurnal-like temporal organization). When the time of feeding coincided with activity offset, normocaloric feeding also synchronized the locomotor activity rhythm with no apparent switch in temporal organization. Peak of Per2 expression in the piriform cortex occurred between the beginning and the middle of the activity/feeding period, depending on the synchronizer. These data demonstrate that even though the suprachiasmatic clockwork can be synchronized to nonphotic cues, hypocaloric feeding likely acts downstream from clock gene oscillations in the suprachiasmatic nuclei to yield a stable yet opposite organization of the rest/activity cycle.

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