Effects Of Nimotop On Brain AQP4 Expression In Young Rats And Blood-brain Barrier Permeability After Severe Scald

Objective: Aquaporin 4(AQP4) is the most widespread aquaporin in brain, and which is important in pathomechanism of brain edema caused by ischemia ,hemorrhage,trauma,tumor etc. Through dynamically observing the brain water content,brain tissues Evan's blue(EB) content, brain AQP4 expression after severe scald,and the changes after the use of nimotop ,this experiment explored the mechanism of brain edema and the intervention mechanism of nimotop after severe scald in order to provide the experimental basis of clinical therapy.Methods: Experiments were performed in seventy-two healthy 1-month-old Sprague-Dawley (SD) rats of either sex, weighing 70~100g. The experimental rats models with severe scald(30% TBSA III degree) were established. The rats were randomly divided into four groups as following: A (normal control group,n=6);B (sham-scalded group,n=6);C (scald group,n=30);D (scald+Nimotop treatment group,n=30),Of which the C and D groups were divided into five time points: 2, 6, 12, 24, and 48h. The brain water content was measured by dry/wet weight; The brain tissues Evan's blue (EB)content were examined with the ultraviolet spectrophotometer; The changes of brain AQP4 expression after severe scald were determined by immunohistochemical method.Results: The brain water content and the expression of brain AQP4 began to increase 2 hours after severe scald, then reached peak after 6 hours,which were still higher than the cotronl groups after 48 hours.The changes of the brain water content were significantly positively correlated with the expression of brain AQP4(r=0.932,P<0.01).The permeability of BBB(EB content be used to evaluate permeability) began to increase 2 hour after severe scald, and reached its peak in 6 hours. The permeability of BBB were positively correlated with expression of brain AQP4 (r=0.969, P<0.05).After nimotop given, the brain water content, permeability of BBB, and expression of brain AQP4 were decreased.Conclusions: The expression of brain AQP4, permeability of BBB, and the brain water content all increased after severe scald.The changes of the AQP4 expression were positively correlated with the permeability of BBB and the brain water content, It had shown that the AQP4 expressions had a significantly positive correlation with brain edema and the damage degree of BBB after severe scald. The up-regulation of brain AQP4 expression after severe scald could increase the permeability of BBB and induced brain water content rised. Given nimotop treatment,compared with the scald group,the AQP4 expression,BBB permeability,and brain water content in the corresponding time points are significant differences(P<0.05).It had shown that nimotop can protect the function of BBB and reduce the degree of brain edema by lowering the AQP4 expression after severe scald.