The importance of controlling in vitro oxygen tension to accurately model in vivo neurophysiology.

The majority of in vitro studies modeling in vivo conditions are performed on the lab bench in atmospheric air. However, the oxygen tension (pO2 ) present in atmospheric air (160mm Hg, ∼21% O2 ) is in great excess to the pO2 that permeates tissues within the brain (5-45mm Hg, ∼1-6% O2 ). This review will discuss the differentiation between pO2 in the in vivo environment and the pO2 commonly used during in vitro experiments, and how this could affect assay outcomes. Also highlighted are studies linking changes in pO2 to changes in cellular function, particularly the role of pO2 in mitochondrial function, reactive oxygen species production, and cellular growth and differentiation. The role of hypoxia inducible factor 1 and oxygen sensing is also presented. Finally, emerging literature exploring sex differences in tissue oxygenation is discussed.