Remodification Of The Cardiac Arrest Model In Rats By Asphyxia Method And Study Of Brain Tissue Aquaporin-4 Expression After Cardiopulmonary Resuscitation

Part I Remodification of the Cardiac Arrest Model in Rats by Asphyxia MethodObjective:To remodify the cardiac arrest model in rat by aspHyxia method.; to investigate the effect of time of cardiac arrest(CA) on the result of resuscitation and BWC at the 6th hour after ROSC.Methods:Thirty-six male SD rats were divided into four groups at random:control group;CA1min group;CA 3min group and CA 5min group. Cardiac arrest was induced in rats by asphyxia. Cardiopulmonary resuscitation(CPR) was executed on 1min,3min,5min after CA,. Dynamic changes of mean arterial pressure(MAP),heart rate (HR)and body temperature were monitored in rats by electrocardio-monitor during the stage of CPR, and the dynamic changes of blood gas were monitored by drawing blood from femoral artery. The time of CPR,the percentage of successful resuscitation and the percentage of survival on third hour after CPR were observed. BWC was measured by means of wet-to-dry weight ratio at 6th hour after ROSC.Results:The percentage of survival on sixth hour after ROSC in the group of CA 3min was significantly higer than that in the group of CA 5min, and the percentage of ROSC in the group of CA3min was remarkably higer than that in the group of CA5min(P < 0.05).The BWC of rats in CA1,CA3min,CA5min groups at the 6th hour after ROSC was significantly higher than those of the control group(P<0.05),and the BWC of rats in CA3min group at the 6th after ROSC was significantly higher than that of the CA1min group(P<0.05).Conclusion:1. The cardiac arrest model after remodification in rat by aspHyxia method was stable. The percentage of ROSC and survival on sixth hour after ROSC was much higher than that before remodification.2.. The CA time play an important role in deciding the percentages of survival and ROSC,the BWC on 6th hour after ROSC.To study the brain edema after ROSC,the time ofPartПStudy on Dynamic Change of Aquaporin-4 and AQP4mRNA Expression Level in the Brain Tissue in Rats and the Effect of Mild Hypothermia on them after Cardiopulmonary ResuscitationObjective:To investigate the dynamic change of brain edema during early stage after ROSC,the role of aquaporin-4(AQP4) and AQP4mRNA in the development of brain edema and the effect of mild hypothermia on them.Methods:Sixty-six male SD rats were subjected to third groups at random :control group;normothermic CA group ;mild hypothermia CA group . The later two groups were respectively divided into ROSC0.5,1,3,6 and 9hours subgroups(n=6).The cardiac arrest model in rats was duplicated by asphyxy method. The brain water content(BWC) was measured by means of wet-to-dry weight ratio at ROSC0.5,1,3,6 and 9hours ,and the BWC was determined by brain wet-to-dry weight ratio at the same time. The AQP4 expression level in brain tissue was determined by semi-quantization immuno- histochemistry staining at the same time. The expression of AQP4-mRNA expression level in brain tissue was measured by RT-PCR. The Correlations were analyzed between the BWC and AQP4 expression level, the BWC and AQP4-mRNA expression level.Results:1. The BWC increased obviously at 0.5h after ROSC in normothermic CA group. The BWC at 0.5,1,3,6 and 9h after ROSC were significantly higher than that of the control group(P<0.05). The change of morphology in brain tissure coincided with the results above.At the same time, the changes of the AQP4 and AQP4mRNA expression level was as nearly same as that of the BWC. The correlation analysis demonstrated further that the BWC was correlated apparently with the AQP4,AQP4mRNA expression level in brain tissue, (r = 0.847,P<0.01)(r = 0.771,P<0.01).2. The BWC and AQP4 expression leve in brain tissue were not significantly different at 0.5h after ROSC between mild hypothermia CA group and normothermic CA group;the two objects observed in mild hypothermia CA rats were much lower than those in normothermic CA rats at 0.5,1,3,6 and 9h after ROSC(P <0.05). The correlation analysis demonstrated that the BWC was also correlated apparently with the AQP4,AQP4mRNA expression level in brain tissue when mild hypothermia was executed on rats for 9h, (r = 0.769,P<0.01)(r = 0.780,P<0.01).Conclusion:1. The brain edema occurs at 0.5h after ROSC , and it gets more and more severe as time goes by.2. The expression level of AQP4 in brain tissue is up-regulated after ROSC, the expression level of AQP4 mRNA is up-regulated as well.. It is indicating that AQP4,AQP4mRNA play probably key role in the development of brain edema.3. Mild hypothermia after ROSC can reduce the development of brain edema in the early stage after ROSC, the mechanism is possibly related to the down-regulation of AQP4 and AQP4 mRNA expression level in brain tissue issued by mild hypothermia.