OBSERVATIONS ON CEREBRAL ISCHEMIA AT INJURY THRESHOLD LEVELS

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Studies on mechanisms, associated with survival of the neurons subjected to ischemia, have important clinical implications, since elucidation of the nature of such mechanisms may ameliorate or prevent brain tissue damage following cerebral ischemia insults. In experimental research, the degree of ischemic injury which allows recovery of affected neurons is called "penumbra", i.e. resembling a twilight zone around solar eclipse. In our studies, we produced conditions of penumbra by subjecting cats to 20 minute occlusion of the middle cerebral artery (MCA) and studying various parameters of ischemic injury up to 2 weeks after the insult. Our studies demonstrated that although the animals showed significant and widespread changes up to 3 days after recirculation, there was either complete or partial recovery with regard to edema and neuronal damage, when animals were examined 2 weeks after MCA occlusion. Our investigations resulted thus in establishing an experimental model where pathomechanisms associated with reversible ischemic damage could be analyzed and, potentially, manipulated.