REGIONAL CEREBRAL BLOOD-FLOW DURING AND AFTER 2 HOURS OF MIDDLE CEREBRAL-ARTERY OCCLUSION IN THE RAT

In this study we explored if the secondary bioenergetic failure, which occurs a few hours after recirculation, following transient middle ce rebral artery occlusion (MCAO) in rats, is caused by a compromised ref low. We induced 2 hours of MCAO and measured CBF at the end of the isc hemia, as well as 15 minutes, 1, 2, and 4 hours after the start of rec irculation, using autoradiographic or tissue sampling C-14-iodoantipyr ine techniques. After 2 hours of MCAO, the autoradiographically measur ed CBF in the ischemic core areas was reduced to 3 to 5% of contralate ral values. The reduction in CBF was less in neighboring, penumbral ar eas. After recirculation, now already normalized in core tissues after 15 minutes, and remained close to normal for the 4 hours recirculatio n period studied. However, in penumbral tissues, recovery CBF values w ere usually below normal. The results show that tissues that are heavi ly compromised by the 2-hour period of ischemia and are destined to in cur infarction, show a ''relative hyperemia'' during recirculation. In fact, some areas of the previously densely ischemic tissue showed ove rt hyperperfusion. This finding raises the question whether the relati ve or absolute hyperemia reflects events that are pathogenetically imp ortant, Because drugs that clearly ameliorate the final damage incurre d fail to alter the relative hyperperfusion of previously ischemic tis sues, it is concluded that vascular events in the reperfusion period d o not play a major role in causing the final damage.