title: Corticosterone rhythmicity in the rat: interactive effects of dietary restriction and schedule of feeding.
abstract: Effects of changes in diet composition and schedule of restricted feeding on the circadian rhythm of plasma corticosterone in the adult rat were examined. Three restricted feeding schedules were used: diet presented 3 hours after lights-on, 1 hour before lights-off or continuously by automated feeder. Animals were paired to controls (consuming 24% protein diet and libitum) and provided 80% of control food intake/g body weight/day. A fourth experimental group was offered 2.4% protein diet ad libitum. Plasma corticoids were measured every 4 hours from 0800 to 0400 hours. Corticoid levels 20 min after food presentation were also determined. Both control and protein-restricted animals displayed a typical circadian rhythm, with corticoids lowest at 0800 hours and a peak at 2000 hours. Animals fed at 0900 hours exhibited a 12-hour shift in peak corticoids, while the circadian rhythm was totally abolished in animals fed by automated feeder. Offering the restricted ration at 1700 hours, however, resulted in a diurnal rhythm similar to that of controls. While pre and post-feeding corticoids were similar in control and protein-restricted animals, a post-feeding suppression was found in all three food-restricted groups. Clearly, the relationship between feeding schedule and diurnal rhythm must not be ignored in nutritional paradigms.
mesh_terms: D000818:Animals; D001835:Body Weight; D002940:Circadian Rhythm; D003345:Corticosterone / Q000097:blood*; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage*; D002149:Energy Intake; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D005509:Food Dispensers, Automatic; D051381:Rats
chemical_list: D004044:Dietary Proteins; D003345:Corticosterone