Protective Effect Of Methylene Blue On Cerebral Ischemia-reperfusion Injury After Cardiac Arrest In Rabbits

Objective: To study the protective effect of methylene blue(MB)on cerebral ischemia-reperfusion injury after cardiac arrest(CA)in rabbits,and to explore the optimal dose.Methods: 50 adult clean-level rabbits were randomly divided into 5 groups,10 in each group.Control group,low-dose MB group(1.0 mg/kg),medium-dose MB group(5.0 mg/kg),high-dose MB group(10 mg/kg).Sham-operated group,control group,low-dose MB group(1.0 mg/kg),medium-dose MB group(5.0 mg/kg),high-dose MB group(10 mg/kg).Establishment of cardiac arrest(CA)CPR model by external electric shock ventricular fibrillation.The concentrations of NSE,S-100βprotein and caspase-3 in brain injury markers were detected in 15 min before debrolation and 1 h,6 h,12 h and 24 h after +ROSC.Animals were sacrificed 24 h after ROSC,brain tissue was taken,brain water content was measured,cerebral infarction volume was observed,and histopathological changes in hippocampal CA1 area were analyzed.Results:(1)Serological index: The concentrations of NSE,S-100β protein and caspase-3 at 1h,6h,12 h and 24 h after the recovery of the spontaneous circulation of the control group were significantly higher than those in the sham operation group.In the low,medium and high dose MB treatment groups,the concentrations of NSE at 6h,12 h and 24 h after spontaneous circulation recovery were lower than the blank control group.The medium-dose MB group NSE concentration was lower than the low-dose MB group at 6h,12 h and 24 h after spontaneous circulation recovery.The low-dose MB group NSE concentration was lower than the high-dose MB group at 6h,12 h and24h after spontaneous circulation recovery.In the low,medium and high dose MB treatment groups,the concentrations of S-100βprotein and caspase-3 were lower than the control group at each checkpoint after +ROSC.The concentrations of S-100 βprotein and caspase-3 in the medium-dose MB group were lower than those in the low-dose MB group at each checkpoint after +ROSC,in the low-dose MB group were lower than those in the high-dose MB group at each checkpoint after +ROSC.(2)Brain tissue water content :The percentage of water content in brain tissue of control group was significantly higher than that in sham operation group.In the three doses of MB treatment group,the percentage of brain tissue water content was lower than that of the control group.The percentage of brain tissue water content in the middle dose MB group was lower than that in the low dose MB group.The percentage of brain tissue water content in the low-dose MB group was lower than that in the high-dose MB group.(3)Brain tissue infarct volume : The number of cerebral infarction volume specimens is too small to be statistically significant.(4)Pathological changes in hippocampal CA1 area: No abnormal abnormalities in neuronal cells in the sham operation group;The neurons in the control group had obvious edema and scattered red neurons;Three doses of MB group had fewer red neuron cells and lessened edema.Medium dose MB group is the lightest lesion.Conclusion: 1 、 MB has a protective effect on cerebral ischemia-reperfusion injury in CA.2、Medium dose MB(5.0 mg/kg)brain protection is more obvious.