The effect of mild hypothermia on reversible middle cerebral artery occlusion in the rat – Effect on regional cerebral blood flow and the therapeutic time window – *
Background and Purpose : Mild hypothermia is possibly the single most effective method of cerebroprotection developed to date, but there have been few reports regarding regional cerebral blood flow (rCBF). In this study, the results of two investigations designed to determine the chronological changes in rCBF under mild hypothermia and their cffccts on infarct size, programmed cell death, and IL 6 bioactivity are presented. Methods : In the first study ( I ), two hours of transient middle cerebral artery occlusion and reperfusion were performed with a rat suture model under normothermic and hypothermic conditions, rCBF was measured during ischemia, 2 hr after reperfusion, and 24 hr after reperfusion. In the second study (Ⅱ), four hours of transient middle cerebral artery occlusion (prolonged ischemic time under hypothermia) and reperfusion were performed under hypothermic conditions, rCBF, infarct size, programmed cell death, and IL- 6 bioactivity were measured 24 hr after reperfusion. Results : Acute post-ischemic hyperperfusion and delayed hypoperfusion in the ischemic core area were inhibited, rCBF was highly maintained in the ischemic penumbra area, no effect in ischemic remote area ( I ). When the repert'usion time was prolonged under mild hypothermia, extension of the infarct region was suppressed by an increase in rCBF. Apoptotic cells were absent in the subcortical cortex, and IL- 6 bioactivity in the ischemic hemisphere did not increase (Ⅱ). Conclusions : These results demonstrated the effect of mild hypothermia on rCBF, and showed that this therapy prolonged the therapeutic time window. (Accepted on July 9 , 2001) Kawasaki Igakkaishi 27( 2 ) : 123-132. 2001
