Effects of time of feeding on recovery of food-entrained rhythms during subsequent fasting in SCN-lesioned rats.
Rats subjected to Eat-Fast (EF) cycles show food-anticipatory rhythms independent from the suprachiasmatic nuclei (SCN). These rhythms do not persist during subsequent ad lib feeding (EE). There are indications for a recovery of rhythmicity during fasting (FF) using a 'memory' paradigm in which FF sessions are alternated with EE. In this study we tested the memory paradigm in SCN-lesioned rats that were fed for 3 hr either during the local day (food access at 14.30 hr) or during the night (food access at 04.30 hr or at 23.00 hr). Food approaches, drinking, wheel-running and body temperature were recorded under constant light. Food-anticipatory rhythms emerged under each EF schedule while the shape of the rhythms differed per schedule. The rhythms disappeared in EE. During subsequent FF the rhythms clearly reappeared in previously day-fed rats, but this was only occasionally observed in previously night-fed rats. Moreover, the phase of the rhythms which did recover in the previously night-fed rats was shifted towards daytime. These data are not fully compatible with the hypothesis of a self-sustained food-entrainable oscillator. It was assumed that hunger-induced responses to environmental daytime stimuli contributed to the overt rhythms.
Ruis
J F
JF
Department of Physiology, University of Leiden, The Netherlands.
Talamini
L M
LM
Buys
J P
JP
Rietveld
W J
WJ
D000818:Animals; D001245:Association Learning / Q000502:physiology*; D001522:Behavior, Animal / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D005508:Food Deprivation / Q000502:physiology*; D007858:Learning / Q000502:physiology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D013493:Suprachiasmatic Nucleus / Q000502:physiology*