Sustained microvascular flow response to functional activation in rat cerebral cortex

The flow response in the cerebral cortex with high spatial resolution during functional activation was examined employing our new optical method. We found that electrical stimulation (ES) of a hind limb increased localized microvascular flow in the contralateral somatosensory cortex in alpha-chloralose-anesthetized SD rats. The spatial microflow increase patterns were heterogeneous, but the size of the increased flow area was almost the same in all five cases studied. The microvascular flow increase was approximately 25% (50% at the central peak decreasing to 5% in the margin) over the cortical area of ca. 1.8 +/- 0.1 mm in diameter. We also found that the time-sequential spatial extents of the activated area of the two-dimensional (2-D) flow maps were coincident with the activated area determined by changes in reflected light intensity. The local microvascular flow increase triggered by cell activation appeared to induce sustained (mismatched) flow in the associated area, even when the activated state of the neurons subsided immediately after the elimination of the peripheral stimuli. (C) 2002 Elsevier Science B.V. All rights reserved.