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Temporal Organization of the Sleep-Wake Cycle under Food Entrainment in the Rat

2016; Oxford University Press; Volume: 39; Issue: 7 Linguagem: Inglês

10.5665/sleep.5982

1550-9109

Javiera Castro-Faúndez, Javier Díaz, Adrián Ocampo-Garcés,

Regulation of Appetite and Obesity

To analyze the temporal organization of the sleep-wake cycle under food entrainment in the rat. Eighteen male Sprague-Dawley rats were chronically implanted for polysomnographic recording. During the baseline (BL) protocol, rats were recorded under a 12:12 light-dark (LD) schedule in individual isolation chambers with food and water ad libitum. Food entrainment was performed by means of a 4-h food restriction (FR) protocol starting at photic zeitgeber time 5. Eight animals underwent a 3-h phase advance of the FR protocol (A-FR). We compared the mean curves and acrophases of wakefulness, NREM sleep, and REM sleep under photic and food entrainment and after a phase advance in scheduled food delivery. We further evaluated the dynamics of REM sleep homeostasis and the NREM sleep EEG delta wave profile. A prominent food-anticipatory arousal interval was observed after nine or more days of FR, characterized by increased wakefulness and suppression of REM sleep propensity and dampening of NREM sleep EEG delta activity. REM sleep exhibited a robust nocturnal phase preference under FR that was not explained by a nocturnal REM sleep rebound. The mean curve of sleep-wake states and NREM sleep EEG delta activity remained phase-locked to the timing of meals during the A-FR protocol. Our results support the hypothesis that under food entrainment, the sleep-wake cycle is coupled to a food-entrainable oscillator (FEO). Our findings suggest an unexpected interaction between FEO output and NREM sleep EEG delta activity generators. The mammalian circadian system times metabolism and behavior within the frame of the 24-hour cycle, determining diurnal, nocturnal or crepuscular phase preference of sleep-wake states. Here we show that a 24 hour eat/fast cycle operates as an efficient time cue for the rat's sleep-wake cycle. The coupling of sleep-wake state generators to scheduled feeding gives support to the notion that the circadian system is composed by a complex array of oscillators that includes a food-entrainable oscillator. This results may help to understand how feeding schedules contribute to the robustness of the output of the circadian system under ecological conditions and, on the other hand, how chronodisruption may emerge as consequence of mistimed feeding.