Cumulative Effects of Repeated Brief Cerebral Ischemia

摘要

The purpose of this grant was to investigate the metabolic and physiologicalfactors determining the extent of the ischemic damage in a model of brief repetitive cerebral ischemia. The model is intended to simulate the effects of Gz induced blackout experienced by fighter pilots undergoing high gravitational stress maneuvers. To achieve this goal a rat model was developed whereby the ischemia was remotely induced by inflation (under computer control) of an occlusive cuff placed about the common carotid artery. Metabolic parameters were determined using in vivo NMR spectroscopy measurements throughout the ischemic and reflow periods. Lactate production was found to be highly reproducible and not limited by blood glucose levels. High energy phosphate decreases were correlated with loss of high frequency EEG. To evaluate the correlation between histologic damage and measures of regional metabolism we have carried out 1H spectroscopic imaging experiments with histologic evaluations of the brain three hours after reperfusion. These studies were acquired with 5 minute (2 dimensional mapping across the cortex) and 16 sec time resolution (1 dimensional mapping ) during the ischemia and reflow. Preliminary results of regional clearance kinetics of lactate shows a strong correlation with the presence of histologic damage. Repetitive Ischemia, EEG, Lactate, Phosphocreatine, pH Magnetic resonance spectroscopy.