BLOOD-FLOW DEPENDENT DURATION OF CORTICAL DEPOLARIZATIONS IN THE PERIPHERY OF FOCAL ISCHEMIA OF RAT-BRAIN

Cortical depolarizations in the periphery of focal ischemia result in metabolic disturbances which contribute to the progression of the isch emic injury. In this experimental study, therefore, it was examined wh ether the duration of peri-infarct depolarizations, which reflects the severity of a metabolic mismatch, is determined by the level of resid ual blood flow in the periphery of focal ischemia. After occlusion of the middle cerebral artery for 3 h, the depolarization time of direct current (DC) shifts was 2.5 +/- 0.7 min at Row rates ranging from 60-1 00% of control increasing discretely to 3.5 +/- 3.2 (ns) min when flow values varied from 40-59%. At flow values below 40% of control, howev er, depolarization time of peri-infarct DC shifts increased significan tly to 25.3 +/- 22.5 min (P < 0.05). These findings suggest that at cr itical flow levels, repetitive penumbral depolarizations cause a sever e disturbance of cell ion homeostasis due to transient intervals of im paired energy metabolism which explains the gradual expansion of the e volving brain infarct. (C) 1997 Elsevier Science Ireland Ltd.