Influence of long-term food restriction on sleep pattern in male rats

The present purpose was to determine the effects of different schedules of long-term food restriction (FR) applied to rats from weaning to the 8th week. Rats were distributed into FR and ad libitum groups at weaning and fed at 7 am, at 7 pm, and finally, restricted rats fed ad libitum. The restricted rats started with 6 g/day and the food was increased by 1 g per week until reaching 15 g/day by adulthood. The rats were implanted with electrodes to record electrocorticogram/eletromyogram signals. Their wake-sleep cycles were monitored over 3 consecutive days (72 h of recording). The FR group fed at 7 am showed an increase in awake time, and decrease in slow wave sleep (SWS) and paradoxical sleep (PS) during the three light periods compared with the control recordings whereas in the dark periods, these sleep parameters were the opposite. The restricted group fed in the evening showed no statistical significances at diurnal periods; however, a significant decrease was observed in the dark recordings for awake time, but the SWS and PS were increased in relation to controls. The analysis of the 24-h period demonstrated that both FR groups presented increase in SWS time. After being FR, the rats were fed ad libitum and their sleep was monitored for 3 additional days. During the first dark recording, the decrease in awake time and increase in SWS were still present; however, as ad libitum food continued, these sleep parameters returned to control values, reestablishing the normal sleep pattern. These results suggest that dietary restriction, regardless to the feeding schedule, caused increase in total sleep time, during the active period.