Mild hypobaric hypoxic postconditioning increases the expression of HIF-1α and erythropoietin in the CA1 field of the hippocampus of rats that survive after severe hypoxia

Using immunohistochemistry, we studied the expression of the alpha regulatory subunit of the hypoxia-inducible factor (HIF-1 alpha) and the product of its target gene, which encodes the protective cytokine erythropoietin in the hippocampal CA1 field of rats in response to damaging severe hypoxia and severe hypoxia followed by three sessions of postconditioning with mild hypobaric hypoxia. We found that the immunoreactivity to the proteins studied in the hippocampus of rats was reduced in response to severe hypoxia. Hypoxic postconditioning sessions of mild hypobaric hypoxia (360 mmHg, 2 h, three times at intervals of 24 h) up regulated the expression of HIF-1 alpha and erythropoietin in hippocampal CA1 neurons of rats that survived after severe hypoxia. Our results indicate that postconditioning led to compensation of hypoxia-induced neuron damage in the brain, which actively involved HIF-1 alpha and erythropoietin.