Effect of Intermittent Hypoxia on the Expression of Glucocorticoid Receptors and Hypoxia-Inducible Factor in Rat Brain.

The effect of intermittent normobaric hypoxia on the expression of hypoxia-inducible factor 1α (HIF-1α) and glucocorticoid receptors in the brain of male Wistar rats was studied in the context of developing neuroprotective methods of hypoxytherapy. Hypoxia in three modes of different effectiveness was modeled by three cycles of 5-min inhalation of a hypoxic mixture (9, 12, or 16% O2) with 15-min intervals of normoxia (21% O2) over 3 days. Immunopositive staining for glucocorticoid receptors and HIF-1α in rat brain increased, which correlated with the protective effectiveness of the regimen. The protective mode (9% O2) increased the expression of these proteins in all regions, the medium mode (12% O2) stimulated expression of glucocorticoid receptors only in layer V of the neocortex and HIF-1α only in the CA1 field. The least effective mode (16% O2) did not affect these parameters. Thus, neuroprotective normobaric hypoxia activates the same adaptive mechanisms as hypobaric hypoxia.