title: Changes in sleep patterns in spontaneously hypertensive rats.
abstract: OBJECTIVE
  To explore whether spontaneous hypertension is associated with a change in sleep pattern in rats.
  
  
  METHODS
  Adult male spontaneously hypertensive rats (SHR) were compared to normotensive Wistar-Kyoto rats (WKY) on their normal daytime sleep pattern.
  
  
  METHODS
  Ten WKY and 10 SHR.
  
  
  METHODS
  All rats had electrodes implanted for polygraphic recordings. Weeks later, a 5-hour daytime sleep-weakfulness recording session was analyzed.
  
  
  RESULTS
  Electroencephalogram and electromyogram signals were subjected to continuous power spectral analysis, from which mean power frequency of the electroencephalogram and power of the electromyogram were quantified. Active waking (AW), quiet sleep (QS), and paradoxical sleep (PS) were defined every 8 seconds from corresponding mean power frequency and electromyogram power readings. Analysis of heart-rate variability was derived from the electrocardiogram signals. Macrostructural analysis of sleep revealed that SHR were characterized by fewer QS and PS episodes and eventually shorter accumulated QS and PS times as compared to WKY. SHR also had more QS-to-AW transitions but fewer QS-to-PS transitions. Microstructural analysis revealed that SHR were associated with more-frequent interruptions during QS. Analysis of heart-rate variability indicated that SHR had similar R-R intervals and lower high-frequency (0.6-2.4 Hz) power but a higher ratio of low-frequency (0.06-0.6 Hz) power to high-frequency power during the daytime recording as compared to WKY.
  
  
  CONCLUSIONS
  As compared to WKY, SHR may have less sleep time, poorer sleep quality, and a greater tendency to wake up from QS. Such changes in sleep may be concomitant with cardiac autonomic changes. Our methodology offers a convenient yet effective way to study the constitution, sequence, and interruption of sleep in the rat.
authors.affiliation: Institute of Neuroscience, Tzu Chi University, Hualien, Taiwan.
authors.forename: Terry B J
authors.initials: TB
authors.lastname: Kuo
authors.forename: Fu-Zen
authors.initials: FZ
authors.lastname: Shaw
authors.forename: Ching J
authors.initials: CJ
authors.lastname: Lai
authors.forename: Chi-Wan
authors.initials: CW
authors.lastname: Lai
authors.forename: Cheryl C H
authors.initials: CC
authors.lastname: Yang
mesh_terms: D000818:Animals; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004576:Electromyography / Q000295:instrumentation; D006973:Hypertension / Q000453:epidemiology*; D008297:Male; D017286:Polysomnography; D051381:Rats; D017208:Rats, Wistar; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation; D020178:Sleep Disorders, Circadian Rhythm / Q000453:epidemiology*