| Objective: To establish a sevoflurane-induced cognitive impairment model in aged rats,and to detect the expression of 5-HT3 receptor,CaMKII,p-CaMKII,CREB,pCREB and PKA in hippocampus of aged rats,and to understand the effects of sevoflurane and 5-HT3 receptor on cognitive function of aged rats and the mechanism of action of 5-HT3 receptor antagonist.Methods: 75 healthy aged SD rats aged 18-20 months,weighing 0.65-0.7kg,were randomly divided into group C1(n=10),group I(n=10)inhaled ether 4h5-HT3,group C2(n=10)injected lateral ventricle Nacl,group S1(n=10)injected anterior lateral ventricle and group S2(n=10)injected 5-HT3 into lateral ventricle after anesthesia.To investigate the effects of sevoflurane and 5-HT3 receptors on cognitive function and the mechanism of action in aged rats,the inhalation concentration of 50% air-oxygen mixture(2L/min)for 4 hours in control C1 group,50% air-oxygen mixture(2L/min)for 4 hours and 2% sevoflurane for 4 hours in experimental group I,and 50% air in control S1 group in the intervention of 5-HT3 receptor antagonists.NACL was injected into the lateral ventricle 4 hours after oxygen mixture(2L/min)and 2% sevoflurane 4 hours.In group S1,5-HT3 receptor antagonist was injected into the lateral ventricle before inhaling air-oxygen mixture(2L/min)for 4 hours and 2% sevoflurane for 4 hours.In group S2,50% air-oxygen mixture(2L/min)was inhaled for 4 hours and 2% sevoflurane for 4 hours,then 5-HT3 receptor antagonist was injected into the lateral ventricle.The Morris water maze test was performed on 75 healthy aged SD rats 6 days before the establishment of the model.The Morris water maze test was conducted again one day after the establishment of the model.The number of times the old rats traveled through the original platform,the residence time of the second quadrant,the escape latency and the swimming distance were recorded.Ten rats were randomly selected to obtain hippocampal tissue on the 1st,3rd and 7th day after modeling.The expression levels of cAMP were measured by Western Blot assay,including CaMKII,p-CaMKII,CREB,p-CREB,PKA,Real-time assay,5-HT3 receptor and Elisa assay.RESULTS: The results of animal behavioral test showed that in the experiment of investigating the effects of sevoflurane and 5-HT3 receptors on cognitive function and its mechanism of action in aged rats,compared with group C 1,the swimming distance and escape latency of group I rats on the first day after anesthesia wereprolonged,the number of times of traversing the original platform was reduced,and the residence time of quadrant I I was shortened(P < 0.05).Compared with group C1,the expression of 5-HT3 receptor,CaMKII,p-CaMKII,CREB,p-CREB,PKA and cAMP in the hippocampus of group I rats decreased on the first day after anesthesia(P < 0.05);the expression of 5-HT3 receptor in the hippocampus increased gradually on the third and seventh days after anesthesia,and the expression of 5-HT3 receptor in the hippocampus was higher on the seventh day than that in group C1(P < 0.05);the expression of CaMKII,p-CaMKII,CREB,CREB,PKA and cAMP increased gradually,and the surface of the hippocampus.The amount was close to that of group C1(P > 0.05).In the experiment of investigating the intervention effect of 5-HT3 receptor antagonist,compared with group C2,the escape latency and swimming distance S of rats in group S1 and S2 were shortened on the first day after anesthesia,the number of times of original platform crossing was increased,and the second quadrant residence time was prolonged(P < 0.05);Real-time,Western Blot and Elisa methods showed that compared with group C2 on the first day after anesthesia,5-HT3 in hippocampus of rats in group S1 and S2 on the first day after anesthesia.The expression levels of receptor,CaMKII,p-CaMKII,CREB,p-CREB,PKA and cAMP were up-regulated(P < 0.05);the expression of 5-HT3 receptor in hippocampus was up-regulated continuously on day 3 and 7 after anesthesia,and the expression of 5-HT3 receptor in hippocampus was higher on day 7 than that in group C2(P < 0.05);the expression of CaMKII,p-CaMKII,CREB,p-CREB and PKA,cAMP were upregulated gradually.CONCLUSION: 2% sevoflurane can cause postoperative cognitive impairment by inhibiting the expression of CaMK II-CREB signaling pathway mediated by 5-HT3 receptor.Moreover,5-HT3 receptor antagonists can improve the cognitive impairment induced by sevoflurane in aged SD rats by mediating CaMKII-CREB signaling pathway. |
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