title: Time course of neuroprotection induced by normobaric hyperoxia in focal cerebral ischemia.
abstract: BACKGROUND
  The purpose of this study was to determine if normobaric hyperoxia (HO) preconditioning offers durable neuroprotection against cerebral ischemia and the role of reactive oxygen species in the ischemic tolerance mechanism.
  
  
  METHODS
  Rats were  divided into four experimental main groups. First main group which was comprised four subgroups, were exposed to 90% HO for 6 days, 4 hours per day and subjected to 60 minutes of right middle cerebral artery occlusion (MCAO) after 2, 5, 10, and 15 days. Second group acted as control, was exposed  to 21% oxygen (RA; room air) in the same chamber, and subjected to 60 minutes of right MCAO. Third main group comprised two subgroups, were exposed to 90% HO for 6 days, 4 hours per day, received normal saline (NS; 2HO+NS) and dimethylthiourea (DT) just before inhaling 90% HO (2HO+DT). Forth  main group was exposed to 21% oxygen (2RA) in the same chamber and received normal saline (2RA+NS) and DT just before inhaling 21% oxygen (2RA+DT). Last two main groups were subjected to 60 minutes of right MCAO after 2 days. After 24-hour reperfusion, neurological deficit score (NDS), infarct  volume, brain water content, and Evans blue extravasations were assessed in all animals.
  
  
  RESULTS
  First main group compared with the RA group, NDS, infarct volume, Brain water content, and Evans blue extravasations were reduced in 2, 5, and 10 days significantly, whereas there was  no difference among groups 2HO+DT, 2RA+DT, and 2RA+NS.
  
  
  CONCLUSIONS
  In the model of transient focal cerebral ischemia, hyperoxia preconditioning induced effective but transient neuroprotective effects.
authors.affiliation: Shahid Beheshti University, GC, Tehran, Iran.
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Bigdeli
authors.forename: Mahdieh
authors.initials: M
authors.lastname: Asheghabadi
authors.forename: Afshin
authors.initials: A
authors.lastname: Khalili
mesh_terms: D000818:Animals; D001812:Blood-Brain Barrier / Q000503:physiopathology; D001929:Brain Edema / Q000209:etiology / Q000517:prevention & control; D002544:Cerebral Infarction / Q000209:etiology* / Q000517:prevention & control*; D004195:Disease Models, Animal; D018496:Hyperoxia / Q000503:physiopathology*; D020244:Infarction, Middle Cerebral Artery / Q000150:complications* / Q000175:diagnosis / Q000473:pathology; D019194:Ischemic Preconditioning; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D009460:Neurologic Examination; D051381:Rats; D017208:Rats, Wistar; D020127:Recovery of Function; D012039:Regional Blood Flow; D013997:Time Factors