Effects And Mechanisms Of Ultrasound Preconditioning On The Brain Injury In A Rat Model Of Cardiac Arrest/ Cardiopulmonary Resuscitation

Objective:1.To establish six minutes CA/CPR model in rats by using a modified method of the epicardical electrical stimulation.2.To investigate the protective effect of ultrasound preconditioning on brain injury after cardiopulmonary resuscitation in a rat model.Method:1.To duplicate CA/CPR model in rats,cardiac arrest was performed in rats by using a modified method of the epicardical electrical stimulation and cardiopulmonary resuscitation operation including chest compression,mechanical ventilation,adrenaline and defibrillation.was given to save rats.Thirty SD rats were randomly divided into two groups: control group(SHAM group)and model group(CA / CPR group).After the model was established,the type of CA and the CA time was counted;the rate of spontaneous circulation recovery and survival rate at 24,48,72 h was recorded;the pathological changes of cerebral cortex and hippocampus at 72 h were observed under optical microscope.2.The rats were randomly divided into 5 groups: SHAM,group(n = 5)、CPR group(n=8)、US group(n=8)、MLA group with US(n=8)、GTS-21 group without US(n=8).Sham group were only given the basic operation.The CA/CPR was given to all the group except the sham group.Ultrasonic pretreatment was given the night before the CA/CPR.MLA(4mg/kg,ip)was given 30 minute before US and VF in MLA group.GTS-21(4mg/kg,ip)was administrated 30 minute before CA/CPR in GTS-21 group.The recovery rate of spontaneous circulation,the survival rate at 72 hours,the frequency of defibrillation,the number of epinephrine,the duration of CPR and the neurological deficit score were recorded;TNF-α and IL-6 at 1,4 and 72 h after resuscitation were detected by ELISA method;The pathological changes of cerebral cortex and hippocampus were observed by HE staining;the expression of α7 n ACh R protein was detected by Western blot.Results:All rats in model group were induced ventricular fibrillation(VF)successfully.After CPR,the rate of ROSC was 73.3%(11/15),survival rate were 46.7%(7/15),33.3%(5/15),13.3%(2/15)at 24 h,48h and 72 h.Compared with CPR group,the survival rate,CPR time,defibrillation frequency,adrenaline frequency,24 h and 48 h NDS score in US group wassignificantly increased(P <0.05),and there was no significant difference in MLA group(P> 0.05).The survival rate,CPR time,defibrillation frequency in GTS-21 group was significantly higher than that in CPR group(P <0.05),while there was no significant difference in the number of epinephrine(p> 0.05).The levels of TNF-α and IL-6 in CPR group were significantly increased at 1h,4h,72 h when compared with SHAM group(P<0.01).Compared with the CPR group,TNF-α and IL-6 levels in the US group were significantly decreased at 1h,4h,72h(P <0.05);while the decline of TNF-α and IL-6levels in MLA group was not obvious(P> 0.05).Compared with CPR group,TNF-α and IL-6 levels in the GTS-21 group were significantly decreased at 1h,4h,72h(P <0.05).In the results of HE staining,compared with SHAM group,the structure of neurons in CPR group was obviously disordered and the number of neuronal necrosis was more.Compared with the CPR group,the number of necrotic neurons in the US group and GTS-21 group decreased significantly(P <0.01),but there was no significant difference between the MLA group and the CPR group(P> 0.05).Compared with the SHAM group,the expression of α7n ACh R protein decreased in the CPR group(p <0.05);Compared with the CPR group,the expression of α7n ACh R protein in the US group increased(P<0.01);There was no significant difference in the expression of α7n ACh R protein between MLA and CPR group(P> 0.05).Compared with the CPR group,the expression ofα7n ACh R protein in the GTS-21 group significantly increased(P <0.01).Conclusion:1.The cardiac arrest type induced by a modified method of the epicardical electrical stimulation mainly was ventricular fibrillation(VF).This method is stable and simple,can be used for basic research in cardiopulmonary resuscitation.2.Inflammatory reaction is involved in the process of brain injury caused by CA/CPR.Ultrasound pretreatment can activate the cholinergic anti-inflammatory pathway by the way of upregulate the expression of α7n ACh R protein,thereby inhibiting the inflammatory response,improving the survival rate and improving the neurological deficit.