Relationship Between Autophagy And Apoptosis On Sevoflurane Induced Cognitive Dysfunction In Aged Rats

Objective: The aim of this study was to evaluate the relationship between autophagy and apoptosis on sevoflurane induced cognitive dysfunction in aged rats.Methods: One hundred and twenty healthy male Sprague-Dawley rats,aged 18 months,weighting 500-550 g,were randomly divided into 4 groups(n=30 each)using a random number table: control group(group C),cognitive dysfunction group(group P),autophagy inhibitor group(group MA)and autophagy agonist group(group R).In group MA and R,autophagy inhibitor(3-MA)1 mg/kg and autophagy agonist rapamycin 2 mg/kg were injected separately through vena caudalis,while the equal volume of normal saline was injected instead in group C and P.Thirty minutes later,group C received no treatment,other 3 groups exposed to 3% sevoflurane for 3 hours.Morris water maze test was performed on 1st day before anesthesia and 3rd and 7th day after anesthesia.Then brains of rats were removed and hippocampal tissues were obtained for detection of apoptosis in hippocampal neurons and hippocampal LC3-Ⅱ and Beclin-1 expression by western blot.The structure of hippocampal neurons was observed under optical microscope and the ultrastructure of hippocampal neurons was observed under transmission electron microscope.Results:1.The results of Morris water maze test showed that there was no significant difference between the 4 groups on escape latency and the frequency of crossing the original platform at 1st day before anesthesia(P >0.05).Compared with 1st day before anesthesia,the escape latency of group P,MA and R rats was prolonged and the frequency of crossing the original platform decreased(P < 0.05).Compared with the group C,the escape latencyof P,MA and R rats was prolonged and the frequency of crossing the original platform decreased at 3rd and 7th day after anesthesia(P < 0.05).Compared with group P,the escape latency of MA group was prolonged and the frequency of crossing platform was reduced.The escape latency of R group was shortened and the frequency of crossing platform was increased at 3rd and7 th day after anesthesia(P < 0.05).2.The results of flow cytometry showed that there was no significant difference in the apoptosis rate of hippocampal neurons in the 4 groups among the four groups at 1st day before anesthesia(P > 0.05).Compared with 1st day before anesthesia,the apoptosis rate of hippocampal neurons in group P,MA and R increased at 3rd and 7th day after anesthesia(P<0.05).Compared with the group C,the apoptosis rate of hippocampal neurons in group P,MA and R increased at 3rd and 7th day after anesthesia(P < 0.05).Compared with the group P,the apoptosis rate of hippocampal neurons in group MA rats increased and the apoptosis rate of hippocampal neurons decreased in group R at 3rd and7 th day after anesthesia(P < 0.05).3.The results of Western blot showed that there was no significant difference in the expression of 1day LC3-II and Beclin-1 among 4 groups at1 st day before anesthesia(P > 0.05).Compared with 1st day before anesthesia,the expression of LC3-II and Beclin-1 in group P,MA and R were down-regulated at 3rd and 7th day after anesthesia(P < 0.05).Compared with the group C,the expression of LC3-II and Beclin-1 in group P,MA and R was down-regulated at 3rd and 7th day after anesthesia(P < 0.05).Compared with group P,the expression of LC3-II and Beclin-1 in group MA was down-regulated at 3rd and 7th day after anesthesia,and the expression of LC3-II and Beclin-1 increased in group R at 3rd and 7th day after anesthesia(P <0.05).4.The results of light microscopy and electron microscopy showed that there was no significant difference in the structure and ultrastructure of the hippocampal neurons in the four groups of aged rats 1 day before anesthesia.The hippocampal neurons in group P,MA and R were injured in differentdegrees after operation.The degree of injury in group MA was heavier than that in group P,and the degree of injury in group R was less than that in group P.Conclusions : The mechanism of sevoflurane induced cognitive dysfunction in aged rats is related to inhibition of autophagy and promotion of apoptosis in hippocampal neurons.