A measurement of partial pressure of oxygen in unanesthetized and unrestrained rats using a chronically implantable fiber optic probe

Several factors such as anesthesia, hypoxia and stress affect the regulation of brain tissue partial pressure of oxygen (PtO2). We developed a methodology to measure brain PtO2 in unanesthetized and unrestrained rats during acute hypoxia before and after high altitude acclimatization. A fiber optic probe was implanted in the parietal cortex of 8 male Wistar rats to measure brain PtO2 while breathing different fractions of inspired oxygen (FiO2). After 28 days of high-altitude acclimatization, brain PtO2 was measured again while breathing the same FiO 2 values in order to observe the effect of high altitude acclimatization on brain oxygenation. The overall brain PtO2 increased 35% (6.5+/-1.5 mmHg) after acclimatization. In addition, a linear relationship between brain PtO2 and FiO2 was demonstrated. This is the first quantitative evaluation of the effects of acute hypoxia on brain PtO2 before and after high altitude acclimatization in awake and unrestrained rats using a fiber optic probe.