A new approach of sleep and feeding behaviors in the laboratory rat

Sleep and feeding patterns were recorded in 24 rats housed in normal laboratory cages (control) and in niche equipped cages with either a foodcup continuously illuminated or not illuminated (experimental) for 10 to 15 consecutive days. The niche conditions brought about a complete disappearance of nibbling, a significant reduction in the daily number of meals (6.8 vs 9.3) and a significant increase in mean meal size. Though the daily food intake remained unchanged, body weight gain was significantly increased. When the foodcup is illuminated, meals were equally distributed between light and dark phases. Parallel to the latter, sleep durations (particularly Paradoxical Sleep) were increased during the dark phase tending towards an equal circadian distribution. Under the niche conditions, meal size was correlated with the post-prandial events (meal-to-meal intervals and sleep durations within them) during the dark phase as it was during the control period. However, unlike control animals, there were also correlations during the light phase. These results suggest that under the niche conditions, there is a stronger physiological (metabolic) motivation of meal taking and sleep occurrence. Henceforth, such an ecological artifact could be used in order to perform experiments aimed at a better understanding of behavioral regulatory mechanisms.