title: Seizures induce phase shifts of rat circadian rhythms.
abstract: BACKGROUND
  Epileptic seizures may alter neuroendocrinological cycles. Light pulses induce phase shifts in circadian rhythms. Using hippocampal-kindled rats to ensure maximal clinical expression, we determined if seizures likewise induce phase shifts.
  
  
  METHODS
  We monitored the circadian rhythm of temperature (CRT) with intraperitoneal radiotelemetry in rats (n=21) isolated from time cues and light for 3-week trials. Seizures were triggered with hippocampal electrical stimulation at different circadian phases. Optimized, least-error phase shifts were calculated from preictal and postictal CRTs. Induced seizures were referenced to CRT (t(max)=00:00, 24-h circadian cycle).
  
  
  RESULTS
  Phase shifts (individual responses=57) differed across the circadian cycle. Rather than forming a clear phase-response curve, phase shifts were especially variable between 00:00 and 06:00 h.
  
  
  CONCLUSIONS
  This study demonstrates that electrically-induced seizures induce advances and delays in CRT in a phase-dependent fashion but in a pattern different from typical light-induced phase shifts. Disorders of circadian regulation may contribute to some of the altered endogenous cycles associated with epilepsy.
authors.affiliation: Comprehensive Epilepsy Program, Department of Neurology, University of Virginia, Box 394, Health Sciences Center, Charlottesville, VA 22908, USA. quigg@virginia.edu
authors.forename: M
authors.initials: M
authors.lastname: Quigg
authors.forename: M
authors.initials: M
authors.lastname: Straume
authors.forename: T
authors.initials: T
authors.lastname: Smith
authors.forename: M
authors.initials: M
authors.lastname: Menaker
authors.forename: E H
authors.initials: EH
authors.lastname: Bertram
mesh_terms: D000818:Animals; D001833:Body Temperature Regulation / Q000502:physiology*; D001921:Brain / Q000473:pathology / Q000503:physiopathology*; D021081:Chronobiology Disorders / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D002940:Circadian Rhythm / Q000502:physiology*; D004558:Electric Stimulation / Q000009:adverse effects; D004827:Epilepsy / Q000150:complications* / Q000473:pathology / Q000503:physiopathology; D007696:Kindling, Neurologic / Q000502:physiology*; D008297:Male; D010775:Photic Stimulation; D051381:Rats; D017207:Rats, Sprague-Dawley