A method for noninvasive measurement of oxygen levels in the brain of living rodents is published this week in Nature Methods. This approach will allow for more detailed studies of vascular regulation and metabolic function in the living brain, in health and disease.
The brain maintains high levels of metabolism, which are sustained by the consumption of large amounts of oxygen. Proper oxygenation is critical for brain function, and it is therefore of high interest to study oxygen delivery to different parts of the brain. Existing methods for mapping oxygen levels in the brain are either invasive and can cause damage or suffer from low spatial resolution.
Using a two-photon-excitable phosphorescent probe either introduced into the vasculature or directly injected into the brain, David Boas and colleagues mapped oxygen deep into the tissue of rodent brains. The phosphorescence of this probe is quenched by oxygen, such that the lifetime of the signal can be used to read out oxygen levels. The authors use this to map oxygen levels in multiple locations within both blood vessels and tissue of living rodent brains, at microscopic resolution and at depths of several hundred micrometers. They examine the effects of transient hypoxia on brain oxygen levels.