title: Mild hypobaric hypoxia preconditioning up-regulates expression of transcription factors c-Fos and NGFI-A in rat neocortex and hippocampus.
abstract: Transcription factors c-Fos and NGFI-A encoded by immediate early genes largely participate in the biochemical cascade leading to genomically driven lasting adaptation by neurons to injurious exposures including hypoxia/ischemia. Present study was designed to examine the involvement of c-Fos and NGFI-A in the development of brain hypoxic tolerance induced by mild hypoxic preconditioning. Earlier we have reported that preconditioning by repetitive mild hypobaric hypoxia (MHH) considerably increases neuronal resistance to subsequent severe injurious exposures. Herein, changes of c-Fos and NGFI-A expression in vulnerable rat brain areas (hippocampus, neocortex) in response to preconditioning MHH itself were studied using quantitative immunocytochemistry. Exposure to MHH differentially enhanced c-Fos and NGFI-A expression in neocortex and hippocampal fields 3-24h following the last MHH trial. The c-Fos up-regulation was the most pronounced in neocortex, CA1, and dentate gyrus, but it was twice lower in CA3/CA4. The up-regulation of NGFI-A in CA1, dentate gyrus and neocortex was 1.5-2-fold lower than that of c-Fos; but in CA3 and CA4 the rates of the c-Fos and NGFI-A induction were comparable. The present findings indicate that cooperative but differential activation of c-Fos and NGFI-A expression in vulnerable brain areas contribute to the development of tolerance achieved by MHH preconditioning.
authors.affiliation: Laboratory of Neuroendocrinology, Pavlov Institute of Physiology, Russian Academy of Sciences. Makarova 6, 199034 St. Petersburg, Russian Federation. samoilov@pavlov.infran.ru
authors.forename: Elena
authors.initials: E
authors.lastname: Rybnikova
authors.forename: Tatiana
authors.initials: T
authors.lastname: Glushchenko
authors.forename: Ekaterina
authors.initials: E
authors.lastname: Tyulkova
authors.forename: Ksenia
authors.initials: K
authors.lastname: Baranova
authors.forename: Michail
authors.initials: M
authors.lastname: Samoilov
mesh_terms: D000818:Animals; D051766:Early Growth Response Protein 1 / Q000096:biosynthesis*; D006624:Hippocampus / Q000378:metabolism*; D020925:Hypoxia-Ischemia, Brain / Q000378:metabolism*; D007150:Immunohistochemistry; D019194:Ischemic Preconditioning / Q000379:methods*; D019579:Neocortex / Q000378:metabolism*; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D015854:Up-Regulation
chemical_list: D051766:Early Growth Response Protein 1; C486110:Egr1 protein, rat; D016760:Proto-Oncogene Proteins c-fos