Perfused microvascular morphometry during middle cerebral artery occlusion.

This study compared the arteriolar and capillary bed perfusion in the ischemic vs. contralateral cortex 1 h after middle cerebral artery (MCA) ligation in anesthetized rat. Fluorescein isothiocyanate (FITC)-dextran identified the perfused vascular beds. Regional cerebral blood flow (CBF) was monitored with [14C]iodoantipyrine. Morphometric parameters were determined through comparisons of the perfused FITC-labeled vessels with alkaline phosphatase-stained preparations of the total microvascular network. Regional CBF was significantly different when the contralateral cortex (54 +/- 7 ml.min-1.100 g-1) (means +/- SE) and the MCA-occluded cortex (31 +/- 8 ml.min-1.100 g-1) were compared. There were no significant regional differences in any morphometric index of structure in the total microvascular bed. The percentage of the total capillary and arteriolar volume that was perfused in the MCA-ligated cortex was significantly lower than the value obtained from the contralateral cortex. The change in the perfusion pattern of the cerebral microvasculature in the ischemic cortex was not due to vessel blockade. The altered temporal perfusion pattern of capillary and arteriolar vessels in the occluded cortex may be due to an altered microvascular perfusion cycle, longer perfusion pathways, vasoconstriction, or partial vessel obstruction.