title: Hypoxic-ischemic tolerance phenomenon observed in neonatal rat brain.
abstract: OBJECTIVE
  Our purpose was to determine whether hypoxic-ischemic brain damage would be protected against by advance conditioning of the animal with 4 hours of hypoxic exposure.
  
  
  METHODS
  Neonatal rats were exposed on postnatal day 7 to (1) 4 hours of hypoxia with 8% oxygen (preconditioning hypoxic group) or (2) 4 hours of normoxia (sham-preconditioning group). At 24 hours after the conditioning, rats from both groups were exposed to left carotid artery ligation followed by 2 hours of hypoxia (8% oxygen/92% nitrogen). All the rats were killed 1 week after hypoxia-ischemia, and their brains were extracted for histologic study.
  
  
  RESULTS
  Two types of brain damage were histologically observed at 1 week after hypoxia-ischemia in both groups: (1) generalized infarction in the ligated hemisphere and (2) predominant neuronal loss in the hippocampal region. The total incidence of brain damage was significantly decreased in the preconditioning hypoxic group (10/24 rats, 41.7%) compared with the sham-preconditioning hypoxic group (17/22 rats, 77.3%; P < .05).
  
  
  CONCLUSIONS
  Our results show that the hypoxic-ischemic tolerance phenomenon may be induced in the hypoxic-ischemic brain damage model by conditioning the animal before the insult with 4 hours of hypoxic exposure.
authors.affiliation: Department of Obstetrics and Gynecology, Miyazaki Medical College, Kiyotake, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Ota
authors.forename: T
authors.initials: T
authors.lastname: Ikeda
authors.forename: K
authors.initials: K
authors.lastname: Abe
authors.forename: H
authors.initials: H
authors.lastname: Sameshima
authors.forename: X Y
authors.initials: XY
authors.lastname: Xia
authors.forename: Y X
authors.initials: YX
authors.lastname: Xia
authors.forename: T
authors.initials: T
authors.lastname: Ikenoue
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001522:Behavior, Animal; D001921:Brain / Q000473:pathology; D002545:Brain Ischemia / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D006624:Hippocampus / Q000473:pathology; D002534:Hypoxia, Brain / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control*; D010100:Oxygen / Q000008:administration & dosage*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D010100:Oxygen