Protective Effect Of Focal Mild Hypothermia On The Brain Against Ischemia-reperfusion BBB Injury In Rat

Objective: To investigate the mechanism of cerebral protection by mild hypothermia against cerebral ischemia and reperfusion, through observation of the changes in the infarct volume and blood-brain barrier(BBB) in rats.Methods: 48 male SD rats weighing 200-250g were randomly divided into 3 groups (n=16 each). Group S: The vertebrobasilar artery and bilateral common carotid arteries will not be occlused, the temperature of the rats would not be mild hypotherature; group R: The male SD rats were subjected to three-vein occlusion : the vertebrobasilar artery and bilateral common carotid arteries would be occlused for 10 min, the rats would not be locall mild hypotherature; group H: The vertebrobasilar artery and bilateral common carotid arteries would be occlused for 10 min, the rats would be locall mild hypotherature(32～35℃) by injecting the 10℃of sodium chloride, then the locall mild hypotherature would be continue 3 hours.The brain tissue samples were taken from rats at 12 hours after reperfusion. There are 8 rats every group were executed and anterior of the right brain were removed for microscopic examination of pathology and electron microscopic examination, then other brain tissue were removed to keep in -20℃liquid nitrogen pot for ultrastrucrure examination and measurement of the content of matrix metalloproteinase-9(MMP-9) in right brain tissue. Left Brain water content was determined by dry-wet weight method.Another 8 rats every group were opened thorax in a hour with injection of EB physiological saline (4ml/kg) in femoral vein When the rats were reperfused for 12 hours. To perfuse physiological saline(P=110mmHg) until the liquid of destrorotation become colorless, then execute the rats and take the whole brain. To removed the cerebellum, pituitary and blood for to measure the content of EB in brain.To detect the change of blood gas at three time points, the blood sample was taken from femoral artery . The first point was taken at 5 min before the brain ischemia, the second was the time of the brain ischemia, the third was the time of 10 min after the reperfusion .Results: MMP-9 were significantly increased in common treatment group after when compared to sham group and hypertension group (P <0.05) . The expression of MMP-9 did not appear in sham-operated group and hypothermia group (P <0.05).The brain water content in the hypertension group is lower than in common treatment group (P <0.05). The data did not appeared in shame group and hypothermia group (P<0.05)The content of EB in brain in the hypertension group is lower than in common treatment group (P <0.05). The data did not appeared in shame- operated group and hypothermia group (P<0.05)Conclusion: These data show that mild hypothermia has protective effect on the brain against I/R injury. It could reduce brain water content (P <0.05), decrease MMP-9 expression.