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 ischemic injury. In this experimental study, therefore, it was examined whether the duration of peri-infarct depolarizations, which reflects the severity of a metabolic mismatch, is determined by the level of residual 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 flow rates ranging from 60-100% 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, however, depolarization time of peri-infarct DC shifts increased significantly to 25.3 +/- 22.5 min (P < 0.05). These findings suggest that at critical flow levels, repetitive penumbral depolarizations cause a severe disturbance of cell ion homeostasis due to transient intervals of impaired energy metabolism which explains the gradual expansion of the evolving brain infarct.
Mies
G
G
Max-Planck-Institute for Neurological Research, Department of Experimental Neurology, Köln, Lindenthal, Germany.
D000818:Animals; D002545:Brain Ischemia / Q000503:physiopathology*; D002536:Cerebral Arteries / Q000502:physiology; D002560:Cerebrovascular Circulation / Q000502:physiology*; D004594:Electrophysiology; D008297:Male; D051381:Rats; D011916:Rats, Inbred F344