Adequacy of Cerebral Vascular Remodeling Following Three Weeks of Hypobaric Hypoxia

Chronic exposure to moderate hypoxia is associated with considerable remodeling of the cerebral microvascular network. In rats exposed to hypobaric (0.5 ATM) hypoxia, cortical microvessel density increases to 171% of controls within the first week. Peak density is reached within two weeks. The increase in hematocrit follows a similar time course. Although the hemodynamic acclimation appears to complete after two weeks, levels of cortical metabolites, obtained after three weeks of exposure, suggest O2 insufficiency at rest. Increased lactate and slightly decreased glycogen concentrations within the brain, along with increased glucose consumption are consistent with an increased dependence on anaerobic glycolysis for energy production. Whatever the production mechanisms, the restored ATP and phosphocreatine levels indicate the energy demand is being met.