Temporal dynamics of the partial pressure of brain tissue oxygen during functional forepaw stimulation in rats

The partial pressure of tissue oxygen (pO(2)) was measured in rat somatosensory cortex during periodic electrical forepaw stimulation of either 1 min or 4 s in duration, and correlated with simultaneous laser Doppler flowmetry. For both stimulus durations, a transient decrease in tissue pO(2) preceded blood flow changes, followed by a peak in blood flow and an overshoot in tissue pO(2) With protracted stimulation, tissue pO(2) remained only slightly above pre-stimulus baseline, while blood flow was maintained at a reduced plateau phase. A sustained post-stimulus undershoot in tissue pO(2) was observed only for the 1 min stimulus. These findings suggest a complex dynamic relationship between oxygen utilization and blood flow. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.