INCREASED FORMATION OF REACTIVE OXYGEN SPECIES AFTER PERMANENT AND REVERSIBLE MIDDLE CEREBRAL-ARTERY OCCLUSION IN THE RAT

In barbiturate-anesthetized rats, we induced 3 hours of permanent midd le cerebral artery occlusion (MCAO) by an intraluminal thread (n = 6), or I hour MCAO followed by 2 hours of reperfusion (n = 6). Through a closed cranial window over the parietal cortex, the production of reac tive oxygen species (ROS) was measured in the infarct border using onl ine in vivo chemiluminescence (CL) while monitoring the appearance of peri-infarct depolarizations (PID). The border-zone localization of th e ROS and direct current (DC) potential measurements was confirmed in additional experiments using laser-Doppler scanning, mapping regional CBF changes through the cranial window after permanent (n = 5) or reve rsible (n = 5) MCAO. CL measurements revealed a short period (10 to 30 minutes) of reduced ROS formation after vessel occlusion, followed by a significant increase (to 162 +/- 51%; baseline = 100%; P < .05) fro m 100 minutes of permanent MCAO onward. Reperfusion after a I-hour per iod of MCAO led to a burst-like pattern of ROS production (peak: 489 /- 330%: P < .05). When the experiments were terminated 3 hours after induction of MCAO, CL was still significantly increased above baseline after permanent and reversible MCAO (to 190 +/- 67%; and 211 +/- 64%, respectively; P < .05). Simultaneous DC potential recordings detected 6.4 +/- 2.7 PID in the first, 4.7 +/- 2.3 in the second, and 2.8 +/- 2.0 in the third hour after permanent MCAO. In animals with reversible MCAO, PID were abolished from IS-minutes recirculation onward. There was no temporal relationship between ROS production and peri-infarct D C potential shifts. In conclusion, using a high temporal resolution RO S detection technique (CL), we found that permanent MCAO (after an ini tial decrease) was accompanied by a steady increase of ROS production during the 3-hour observation period, while reperfusion after 1 hour o f MCAO produced a burst in ROS formation. Both patterns of ROS product ion were not related to the occurrence of PID.