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Food entrainment of clock genes in peripheral tissues and anticipatory response in the liver of rats maintained under a restricted feeding schedule have suggested that the liver may be a relevant element for a food entrained oscillator (FEO). Recent data suggest that mechanisms underlying food-entrainment for metabolic and behavioral or locomotor food anticipatory activity may depend on different regulatory systems. In a previous study we reported that a dysfunctional liver does not prevent animals from exhibiting behavioral anticipatory activity associated with restricted feeding schedules (RFS). The present study aimed to determine whether in CCl4 cirrhotic rats metabolic parameters are entrained to RFS. Chronic CCl4 treated cirrhotic rats and oil treated controls were entrained to RFS. After 2 weeks, rats were sacrificed 2 and 0?h before and 2 and 4?h after mealtime. Serum glucose and free fatty acids were determined as well as liver glycogen. Both groups exhibited a similar entrained pattern in the three parameters. Thus we conclude that anatomical and functional alterations produced by chronic administration of CCl4 do not interfere with entrainment of metabolic parameters to RFS and point out the relevance of other mechanisms independent of the liver to drive peripheral food entrained rhythms. [ABSTRACT FROM AUTHOR]

The present study aimed to identify the hypothalamic nuclei involved with food entrainment by using c-Fos-like immunoreactivity (c-Fos-IR) as a marker of functional activation. We studied rats entrained 3 wk to restricted feeding schedules (RF), their ad libitum (AL) controls, and the persistence of c-Fos-IR temporal patterns in entrained-fasted rats. In addition, we included 22-h fasting and 22-h fasting-refeeding groups as controls of fasting and refeeding acute effects. Diurnal patterns of c-Fos-IR were observed in the tuberomammilar nucleus (TM) and suprachiasmatic nucleus (SCN) in AL rats. In all nuclei, except the SCN and ventromedial nucleus (VMH), restricted feeding schedules imposed a temporal pattern of increased c-Fos-IR around mealtime. An increase in c-Fos-IR before and after meal time was observed in dorsomedial nucleus (DMH), lateral nucleus (LH), perifornical area (PeF), and TM, and a marked increase was observed in the paraventricular nucleus (PVN) after feeding. Food-entrained c-Fos-IR patterns persisted after 3 days in fasting in DMH, LH, and PeF. Present data suggest that FEO might not rely on a single nucleus and rather may be a distributed system constituted of interacting nuclei in which the PVN is mainly involved with the response to signals elicited by food ingestion and, therefore, with the entraining pathway. We can suggest that the PeF and TM may be involved with the arousal state during food anticipation and the DMH and LH with the time-keeping mechanism of FEO or its output. [ABSTRACT FROM AUTHOR]

Food anticipatory activity (FAA) is the expression of a food entrained oscillator, which manifests under restricted feeding schedules (RFS). Food restriction to 2?h daily represents a metabolic challenge and requires behavioral and physiological adaptations in order to allow animals to ingest sufficient food for a 24?h cycle in a short 2?h interval. In order to characterize the behavioral and physiological adaptations during restricted feeding, rats were maintained for 3 weeks under a fixed RFS, an unpredictable RFS and ad libitum (AL) feeding conditions. Feeding behavior was recorded for 2?h during meal access for RFS groups and during the first 2?h of the dark period in AL controls. Body and stomach weight were also measured for the three feeding groups. There was a significant difference between restricted groups and AL controls in the latency and duration of feeding during the 2?h of food access. Restricted rats which could predict mealtime showed the shortest latency. In both RFS groups the stomach attained a large distension in contrast to AL controls, and total time spent in food ingestion was 3?–?4 fold higher than the AL. However, and despite these behavioral and physiological adaptations, restricted rats did not achieve a body weight gain at the end of the experiment, unlike the AL group. Present data indicate that during RFS rats develop behavioral and physiological adaptations to ingest increased amounts of food in a short interval. [ABSTRACT FROM AUTHOR]