The Dynamic Change Of Autophagy In The Tissue Of Cerebral Cortex And Hippocampus Following Cardiac Arrest In Rats

Objective1. To compare cardiac arrest models induced by asphyxiation and induced by transcutaneous electrical epicardium stimulation according to Utstein style. And to observe the rat’s histopathology changes 24 hours after return of spontaneous circulation.2. To observe the rat dynamic autophagy changes in the tissue of cortex and hippocampus following cardiac arrest, and explore the characteristic changes of autophagy after cardiopulmonary resuscitation.Methods1、Using asphyxiation(asphyxia group) and transcutaneous electrical epicardium stimulation(fibrillation group) respectively to establish rat cardiac arrest model. Compared the differences of cardiac arrest induced time, neurological deficit scores, cardiac arrest electrocardiogram change, success rate of resuscitation and survival rate of 24 hours after return of spontaneous circulation between the two groups. And observe the characteristic of histopathological changes between the two groups 24 hours after return of spontaneous circulation.2、Using transcutaneous electrical epicardium stimulation methods to establish rat cardiac arrest model. Successful resuscitation rats were randomly divided into seven groups according to the time point after return of spontaneous circulation: 0h group(sham group), 3h group, 6h group, 12 h group, 24 h group, 48 h group and 72 h group. Rats were sacrificed 3h,6h,12 h,24h,48 h or 72 h after they were return of spontaneous circulation. Using TEM to observe autophagy ultra structural changes. Using western blot and immunohistochemical to detect changes of autophagy related proteins as Beclin-1 and LC3 in the brain cortex and hippocampus.Results1、The time duration from suffocation began to appear cardiac arrest was significantly shorter in the fibrillation group, which was 2.5±1.2 seconds, than that in the asphyxia group, which was 292.7±51.5seconds(P<0.05). Rat electrocardiogram shows asystole of 5 cases and pulseless electrical activity of 10 cases in the asphyxia group. In the fibrillation group, 6 cases show ventricular fibrillation, 7 cases show asystole and 2 cases show pulseless electrical activity. Resuscitation success cases were 6 in the asphyxia group and 4 in the fibrillation group. Survival case were 4 in the asphyxia group and 9 in the fibrillation group 24 h after return of spontaneous circulation. The NDS was significantly lower in the asphyxia group than fibrillation group in the 12 h time point(P < 0.05), and so was it in the 24 h time point(P < 0.05). HE staining shows the nerve tissue pathological changes were more obvious in the asphyxia group than fibrillation group.2、By using TEM to observe ultrastructure changes in the fibrillation cardiac arrest model, we found that autophagosome began to appear from the 6 h, increases to the peak at 24 h and gradually reduce at the 48 h. By using western blot and immunohistochemical to detect changes of autophagy related proteins, which were Beclin-1 and LC3, we found that two proteins expression gradually to increase after the return of spontaneous circulation, and increased to the peak at the 24 h.Conclusion:1. The time to induce cardiac arrest was significantly shorter by using fibrillation than by asphyxia method. The electrocardiogram(ECG) type was more similar to the clinical by using the fibrillation method. The success rate of cardiopulmonary resuscitation and 24 h survival rate were higher in the fibrillation group than asphyxia group. Fibrillation method is the ideal experimental model of cardiopulmonary resuscitation.2. Autophagy is activated following cardiopulmonary resuscitation, and continued for a period of time, suggesting that autophagy plays a certain role in the rat brain damage after cardiac arrest.