Effect of local hypothermia on the infarct volume and β-amyloid protein expression after focal cerebral ischemia and reperfusion in rats

Objective To observe the effect of local intraischemic and postischemic hypothermia on cerebral infarction and expression of β-amyloid protein(Aβ) after focal cerebral ischemia/reperfusion injury in rats.Methods The rat models of cerebral ischemia/reperfusion injury were induced by middle cerebral artery occlusion(MCAO).The rats were randomly divided into sham operation group,normothermia ischemia/reperfusion group and hypothermia ischemia/reperfusion group.The two ischemia/reperfusion groups were further divided into 5 subgroups(subjected ischemia for 2,3,6,8,12 h respectively and then reperfused for 4 h).Brain mild hypothermia started at 30 minutes after the ischemic onset and maintained throughout the periods of ischemia and reperfusion in hypothermia ischemia/reperfusion group.The neurological deficit scores was assessed,and the expression of Aβ was detected with immunohistochemistry.TUNEL method was used to analyze the neuron apoptosis,and the infarct volume was evaluated using 2,3,5-triphenyl-tetrazolium chloride(TTC) staining.Results Compared with the normothermia ischemia/reperfusion group,the infarct volume,expression of Aβ,and apoptosis of neurons were significant reduced in the hypothermia ischemia/reperfusion group(P0.05).The neurological deficit scores in the hypothermia ischemia/reperfusion group was significantly lower than that in the normothermia ischemia/reperfusion group(P0.05 or P0.01).Conclusion The focal mild hypothermia might reduce the infarct volume and accelerate the recovery of the neurological function,which might be related with inhibition of Aβ expression and the anti-apoptosis function.