CHARACTERIZATION OF THE MICROCIRCULATION DURING ISCHEMIA AND REPERFUSION IN THE PENUMBRA OF A RAT MODEL OF TEMPORARY MIDDLE CEREBRAL-ARTERYOCCLUSION - A LASER-DOPPLER FLOWMETRY STUDY

The dynamic changes in microcirculation were investigated with laser D oppler flowmetry in two selected regions of interest (ROI) of a stroke lesion during ischemia and early reperfusion using a rat model of tem porary middle cerebral artery (MCA) occlusion. In each ROI measurement s were made either during 30 min or 2 h of MCA occlusion followed by 1 h of reperfusion. On the periphery of the MCA territory, an area of m ild ischemia with a mean reduction of now to 38% (39.9% in the group w ith 30 min MCA occlusion and 35.9% in the group with 2 h MCA occlusion ) of preischemic values was demonstrated. Closer to the center of the MCA territory, more severe ischemia with a mean reduction of flow to 2 1% (19.9% in the 30-min group and 22.9% in the 2-hour group) was seen. In the two groups with laser Doppler flowmetry in the ROI of mild isc hemia, a compensatory increase in flow during the first 3-6 min after MCA occlusion could be seen. All rats displayed a peak hyperperfusion immediately after re-establishing of flow which then stabilized above, below, or equal to the preischemic level. This peak hyperemia was mos t abundant in the group in which flow was measured in the ROI of more severe ischemia after the 30-min MCA occlusion. In the same area a sho rt hyperemic peak was followed by a significant hypoperfusion of 60% o f preischemic flow after 2 h of MCA occlusion. In the groups with flow measurements in the ROI of mild ischemia, there was a return to preis chemic flow after the 30-min ischemia and a tendency of preserved hype remia after 2 h of MCA occlusion.