title: Short-term homeostasis of REM sleep throughout a 12:12 light:dark schedule in the rat.
abstract: OBJECTIVE
  Intervals extending from the end of a rapid eye movement (REM) sleep episode until the triggering of the next tend to be longer when they follow a longer REM sleep episode. A short-term REM sleep homeostatic process has been hypothesized to explain this effect. The present study assessed and modeled the REM sleep episode-interval relationship and compared its expression at different phases of a 12:12 light: dark schedule.
  
  
  METHODS
  Chronically implanted rats were continuously recorded for 3 consecutive days. Automated state scoring in 15-second epochs determined lengths of REM sleep episodes and intervals and non-rapid eye movement sleep and wakefulness content of intervals.
  
  
  METHODS
  Individual sound-attenuated temperature-regulated boxes.
  
  
  METHODS
  16 Sprague-Dawley rats.
  
  
  METHODS
  Scheduled 12:12 light:dark cycle.
  
  
  RESULTS
  The effect of REM sleep episode length is evidenced by a rising trend in the means and robust means of intervals and non-rapid eye movement content that follow REM sleep episodes of a given length. The relationship of robust means of intervals and REM sleep episode length was best fitted by a Gompertz sigmoid function. The parameters of the Gompertz equation were modulated throughout the 24 hours, presenting the highest amplitude and earliest rise in hours 1 to 4 after lights on and the lowest amplitude at the start of lights off. The modulation was also evident when only intervals with less than 3 minutes of wakefulness were considered.
  
  
  CONCLUSIONS
  Short-term REM sleep homeostasis is modulated throughout the 24 hours under a 12:12 light:dark regime. Its assessment may provide a useful measure of REM sleep propensity, regulation, and recurrence.
authors.affiliation: Laboratorio de Sueño y Cronobiología, Facultad de Medicina, Universidad de Chile, Santiago. evivaldi@machi.med.uchile.cl
authors.forename: Ennio A
authors.initials: EA
authors.lastname: Vivaldi
authors.forename: Adrián
authors.initials: A
authors.lastname: Ocampo-Garcés
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Villegas
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D006624:Hippocampus / Q000502:physiology; D006706:Homeostasis / Q000502:physiology*; D008297:Male; D009334:Neck Muscles / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012894:Sleep Stages / Q000502:physiology; D012895:Sleep, REM / Q000502:physiology*; D013997:Time Factors; D014851:Wakefulness / Q000502:physiology