PT  - JOURNAL ARTICLE
AU  - Devor, Anna
AU  - Sakadžić, Sava
AU  - Saisan, Payam A.
AU  - Yaseen, Mohammad A.
AU  - Roussakis, Emmanuel
AU  - Srinivasan, Vivek J.
AU  - Vinogradov, Sergei A.
AU  - Rosen, Bruce R.
AU  - Buxton, Richard B.
AU  - Dale, Anders M.
AU  - Boas, David A.
TI  - “Overshoot” of O<sub>2</sub> Is Required to Maintain Baseline Tissue Oxygenation at Locations Distal to Blood Vessels
AID  - 10.1523/JNEUROSCI.1968-11.2011
DP  - 2011 Sep 21
TA  - The Journal of Neuroscience
PG  - 13676--13681
VI  - 31
IP  - 38
4099  - http://www.jneurosci.org/content/31/38/13676.short
4100  - http://www.jneurosci.org/content/31/38/13676.full
SO  - J. Neurosci.2011 Sep 21; 31
AB  - In vivo imaging of cerebral tissue oxygenation is important in defining healthy physiology and pathological departures associated with cerebral disease. We used a recently developed two-photon microscopy method, based on a novel phosphorescent nanoprobe, to image tissue oxygenation in the rat primary sensory cortex in response to sensory stimulation. Our measurements showed that a stimulus-evoked increase in tissue pO2 depended on the baseline pO2 level. In particular, during sustained stimulation, the steady-state pO2 at low-baseline locations remained at the baseline, despite large pO2 increases elsewhere. In contrast to the steady state, where pO2 never decreased below the baseline, transient decreases occurred during the “initial dip” and “poststimulus undershoot.” These results suggest that the increase in blood oxygenation during the hemodynamic response, which has been perceived as a paradox, may serve to prevent a sustained oxygenation drop at tissue locations that are remote from the vascular feeding sources.