title: Induction of NADPH-diaphorase activity in the hippocampus in a rat model of cerebral ischemia and ischemic tolerance.
abstract: Preconditioning of the brain with sublethal ischemia induces tolerance to subsequent lethal periods of ischemia (ischemic tolerance). In this study, we used NADPH-diaphorase histochemistry to investigate the postischemic changes of nitric oxide synthase (NOS) in the hippocampus in a rat model of cerebral ischemia and ischemic tolerance. Forebrain ischemia was induced by 4-vessel occlusion for 3 min as an ischemic preconditioning. Three days after the preconditioning or sham operation, second ischemia was induced for 6 min. A transient increase in NADPH-diaphorase activity, beginning after 2 h and maximal after 1 day, was observed in CA1 pyramidal neurons of rats subjected to 3 min of preconditioning ischemia as well as 6 min of subsequent ischemia both with and without preconditioning. In addition, expression of NADPH-diaphorase activity was seen in reactive glial cells in the damaged CA1 region of animals subjected to 6 min of ischemia without preconditioning. Thus, direct involvement of increased NADPH-diaphorase activity in ischemic tolerance was not suggested because the increased NADPH-diaphorase activity preceded the induction of ischemic tolerance which takes place 1-7 days after preconditioning. However, the present findings suggest that the induction of neuronal NADPH-diaphorase activity occurs in response to cerebral ischemia.
authors.affiliation: Department of Neurology, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kato
authors.forename: K
authors.initials: K
authors.lastname: Kogure
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: T
authors.initials: T
authors.lastname: Araki
authors.forename: Y
authors.initials: Y
authors.lastname: Itoyama
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis; D000818:Animals; D003213:Conditioning, Psychological / Q000502:physiology; D006624:Hippocampus / Q000201:enzymology / Q000473:pathology*; D006651:Histocytochemistry; D002546:Ischemic Attack, Transient / Q000201:enzymology / Q000473:pathology*; D008297:Male; D009252:NADPH Dehydrogenase / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase; D017966:Pyramidal Cells / Q000201:enzymology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D009252:NADPH Dehydrogenase