HYPERGLYCEMIA DELAYS TERMINAL DEPOLARIZATION AND ENHANCES REPOLARIZATION AFTER PERIINFARCT SPREADING DEPRESSION AS MEASURED BY SERIAL DIFFUSION MR MAPPING

We investigated the effect of hyperglycemia on the initiation and prop agation of spreading depression-like periinfarct ischemic depolarizati on (SD) induced by focal cerebral ischemia in rats. Peri-infarct SD we re monitored during the initial 15 minutes after remotely induced midd le cerebral artery occlusion (MCAO) using serial diffusion weighted ma gnetic resonance imaging. Maps of the apparent diffusion coefficient ( ADC) were calculated and ADC decreases were monitored over time, Hyper glycemic rats (n = 6) had a significant prolongation of the time from induction of MCAO to the start of the ADC decrease as compared with no rmoglycemic control rats. The time to the maximal ADC decrease was sig nificantly delayed and recovery of transient ADC declines in the area adjacent to the ischemic core was significantly faster in hyperglycemi c rats. We conclude that hyperglycemia delays the terminal depolarizat ion in the ischemic core and supports a faster repolarization in sever ely mal-perfused penumbral tissue after SD, which reflects the increas ed availability of energy substrates in the state of hyperglycemia.