Effects of Protein Malnutrition on Vigilance States and their Circadian Rhythms in 30-Day-Old Rats Submitted Total Sleep Deprivation

Abstract

This study examined how chronic protein malnutrition (6% casein diet) affected the electrocorticogram (ECoG) in young rats following 24 h of sleep deprivation. Baseline (basal day) ECoG-polygraphic recordings were obtained in Sprague-Dawley rats after which animals were sleep-deprived for 24 h by means of a slowly rotating cylinder. ECoG recordings were subsequently obtained for a further three days of recovery. Body weight was significantly reduced in malnourished rats from postnatal day 4 until 34. On basal day, malnourished rats showed a significant increase of slow wave sleep (SWS) during the light and dark phases of the circadian period, and over the 24 h of recording in comparison to control rats. Also, rapid eye movement sleep (REMS) was significantly increased in these rats during the 12-h dark phase of basal day, but wake ECoG activity was significantly reduced during both light and dark phases and over the 24 h of recording, as a result of sleep increases. After sleep deprivation, young malnourished rats failed to show any significant SWS rebound and, unlike control rats, they did not regain pre-deprivation SWS levels within the 3-day post-deprivation recovery period. Further, malnourished rats also failed to have a significant REMS rebound, especially during the dark phase. These results show an important alteration produced by protein malnutrition in the homeostatic and circadian control of vigilance states before and after sleep deprivation.

Keywords:

• Circadian rhythms
• Malnutrition
• REM sleep rebound
• SWS rebound
• Total sleep deprivation
• Vigilance states