EFFECT OF MILD HYPOTHERMIA ON THE CHANGES OF CEREBRAL BLOOD-FLOW, BRAIN-BLOOD BARRIER AND NEURONAL INJURIES FOLLOWING REPERFUSION OF FOCAL CEREBRAL-ISCHEMIA IN RATS

Objective To compare the effects of mild hypothermia induced in differ ent time courses on rats subjected to 3 hours (h) of ischemia followed by 3 h or 72 h of reperfusion. Methods Eighty male Sprague-Dawley rat s were divided into three mild hypothermic (MHT, 32 +/- 0.2 degrees C) groups, including intra-ischemia (MHTi), intra-reperfusion (MHTr), an d intra-ischemia/reperfusion (MHTi + r) group, and one normothermic gr oup (NT, 37 +/- 0.2 degrees C) as the control. Reversible focal ischem ia was carried out in rats with suture model. The cortical blood flow was measured during 3 h of ischemia followed by 3 h of reperfusion. Th e permeability of brain brood barrier (BBB) was estimated after 3 h of reperfusion. The infarct volume was measured at 72 h after reperfusio n to determine the effects of MHT. Results The acute post-ischemic hyp erperfusion and delayed hypoperfusion in ischemic perifocal region and sustained hypoperfusion in ischemic core were inhibited in MHTi + r a nd MHTi rats (P < 0.05). MHTi + r protection on post-ischemic progress ive hypoperfusion in the perifocal region was more effective than that of MHTi (P < 0.05). The BBB disruption and the infarct volume were si gnificantly reduced in both MHTi and MHTi + r groups (P < 0.05), espec ially in the MHTi + r rats. Conclusions This study demonstrates that M HTi + r has more substantial protective effects on reducing ischemia/r eperfusion injury than MHTi. If may inhibit post-ischemic hyperperfusi on and delayed or sustained hypoperfusion in ischemic perifocal region s, and reduce brain blood barrier disruption in the cortex region.