title: Lesion size and behavioral deficits after endothelin-1-induced ischemia are not dependent on time of day.
abstract: BACKGROUND
  The occurrence of stroke exhibits a strong circadian pattern with a peak in the morning hours after waking. The factors that influence this pattern of stroke prevalence may confer varying degrees of neuroprotection and therefore influence stroke severity. This question is difficult to address in clinical cases because of the variability in the location and duration of the ischemic event.
  
  
  METHODS
  The purpose of this study was to determine if time of day affected the severity of stroke targeting the motor cortex in rats. Strokes were produced using topical application of the vasoconstrictor endothelin-1 to motor cortex of unanesthetized animals at 2 time points: early day and early night. Behavioral deficits were measured using reaching, cylinder, and horizontal ladder tasks, and the volume of the lesion was quantified.
  
  
  RESULTS
  Behavior on reaching and horizontal ladder tasks were both severely impaired by endothelin-1 treatment compared to vehicle-treated animals, but deficits did not differ according to time of treatment. Similarly, while endothelin-1 produced larger lesions of the motor cortex than did vehicle treatment, the size of the lesion did not differ according to time of treatment.
  
  
  CONCLUSIONS
  These results suggest that while many factors under circadian control can influence the prevalence of stroke, the magnitude of lesion and behavioral deficit resulting from an ischemic event may not be influenced by time of day.
authors: Department of Psychology, University of Calgary, Calgary, Alberta, Canada.
authors: Brooke D
authors: BD
authors: Rakai
authors: Michael C
authors: MC
authors: Antle
mesh_terms: D000818:Animals; D001522:Behavior, Animal; D002545:Brain Ischemia / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology / Q000523:psychology; D002940:Circadian Rhythm; D004195:Disease Models, Animal; D019332:Endothelin-1; D009043:Motor Activity; D009044:Motor Cortex / Q000473:pathology* / Q000503:physiopathology*; D051381:Rats; D020318:Rats, Long-Evans; D020521:Stroke / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology; D013997:Time Factors
chemical_list: D019332:Endothelin-1