Hypoxia Exposure and Mild Stress on Cell Proliferation and Early Neurogenesis in Dentate Gyrus

Abstract

In the context of animals' age, hypoxia exposure may produce increases or decreases in cell proliferation and neurogenesis in the dentate gyrus (DG). Likewise, hypoxia preconditioning and postconditioning may buffer or potentiate stress-altered cell proliferation or neurogenesis in DG. This study was undertaken to determine the modulating effect of a brief hypoxia regimen (10%- oxygen supply for 30 min at 24 ± 1°C followed by a 6.5- or 7.5-h reoxygenation) on new cell proliferation and early neurogenesis in adult mouse DG. Likewise, we sought to assess the interactive effects of such hypoxia regimen and a mild stressor regimen (a 30-min restraint, immersed in water) in this regard. We found that exposure to the hypoxia regimen with a 7.5-h, not 6.5-h, reoxygenation prior to mouse euthanasia induced reliable increases in the number of newly proliferated cell and proliferative neuroblast in DG, while did not affect neuronal lineage commitment. The mild stress regimen alone did not alter cell proliferation or early neurogenesis in DG, while such mild stress regimen prevented hypoxia-induced increases in cell proliferation and early neurogenesis in DG. These findings, taken together, prompt us to conclude that long post-hypoxia reoxygenation period is required for the emergence of brief hypoxia-induced cell proliferation-and neurogenesis-boosting effects. Moreover, post-hypoxia stress, although stress alone does not affect cell proliferation or neurogenesis in DG, may prevent brief hypoxia-induced cell proliferation- and neurogenesis-boosting effects.