Effects Of Mild Hypothermia On The AQP4 Expression And Brain Edema Following Focal Cerebral Ischemia-reperfusion In Rats

Objective To explore the neuroprotective mechanism of mild hypothermia by studying the effect of mild hypothermia on the aquaporin4(AQP4) expression and brain edema following focal cerebral ischemia-reperfusion in rats.Methods The middle cerebral artery (MCA) of Sprague-Dawley rat was occluded for 2 hours by using the intraluminal suture method and then recirculated at 48 hours postischemia. The rats were randomly assigned to sham-operated group(Sham), normthermic group(NT) and intraischemic hypothermia(IH). The rats were decapitated and brain tissue was collected. The infarction volume was investigated by 2,3,5-Triphenyl tetrazolium chloride (TTC) coloring. The histological morphlogical damage was investigated by hematoxylin-eosin (HE) staining. The permeability of blood-brain barrier (BBB) was evaluated based on leakage of Evans blue. Cerebral edema formation was determined by brain water content. The expression of AQP4 in brain tissue was observed by immunohistochemistry.Results 1. Mild hypothermia significantly ameliorated the histopathological damage in brain and reduced the infarct size. 2. At 48 hours postischemia, brain water content, EB content and AQP4 immunoreactivity were significantly increased in normthermic group. 3. Mild hypothermia significantly decreased brain water content and EB content in brain. Futhermore , mild hypothermia significantly inhibited AQP4 expression.Conclusion 1. The rat model of focal cerebral ischemia-reperfusion made by using the intraluminal suture was sucessful. 2. The breakdown of blood-brain barrier and cerebral edema formation occurred 48 hours postischemia. AQP4...