Characteristics of the transcription factor HIF-1α expression in the rat brain during the development of a depressive state and the antidepressive effects of hypoxic preconditioning

Abstract

The dynamics of HIF-1α expression during the development of stress-related depression, as well as after hypoxic preconditioning (HP), which has an antidepressant-like effect, were studied in the hippocampus, paraventricular hypothalamic nucleus, and neocortex of rats, using an immunocytochemical method. It has been found that the factor HIF-1α is induced in neurons in response to psychoemotional stress that causes the development of experimental depression in rats in the “learned helplessness” model. The profile of the stress-induced expression of HIF-1α in the hippocampus has a two-wave character: early expression on the first day and the delayed expression 10 days after the stress. No significant change was found in the neocortex. In the hypothalamus, up-regulation of HIF-1α expression was delayed (5–10 days). After HP by a moderate repetitive hypobaric hypoxia, which prevents the development of the depressive state in rats, the post-stress expression of HIF-1α was considerably altered in the brain regions studied. In the hippocampus of HP rats, the peak of the early expression lasted for about 5 days after the stress; we observed a multifold increase in its amplitude. In contrast, the HIF-1α delayed peak was eliminated. A similar but smaller effect of HP was also observed in the hypothalamus. The data obtained indicate that delayed HIF-1α expression in the hippocampus and hypothalamus was apparently involved in the mechanisms of pathogenesis of the depressive pathology. However, strong modifications in early and late post-stress expression of HIF-1α caused by HP obviously play an important role in increasing the brain’s tolerance to severe stresses and protection against the development of stress-induced depressive pathologies.