Timed hypocaloric feeding and melatonin synchronize the suprachiasmatic clockwork in rats, but with opposite timing of behavioral output.
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.
Caldelas
Ivette
I
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.
Feillet
Celine A
CA
Dardente
Hugues
H
Eclancher
Françoise
F
Malan
André
A
Gourmelen
Sylviane
S
Pévet
Paul
P
Challet
Etienne
E
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D001683:Biological Clocks / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D005247:Feeding Behavior / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D017403:In Situ Hybridization / Q000379:methods; D008027:Light; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D013997:Time Factors
D008550:Melatonin