Effect of emulsified isoflurane anesthesia on expression of hippocampal amyloid-beta protein and phosphorylation of Tau protein in rats

Objective To investigate the effect of emulsified isoflurane anesthesia on the expression of hippocampal amyloid-beta protein (Aβ) and phosphorylation of Tau protein in rats.Methods Seventy-two healthy Sprague-Dawley rats,aged 8 weeks,weighing 250-300 g,were randomly divided into 3 groups:normal control group (group C,n =12),fat emulsion group (group E,n =12),and 8％ emulsified isoflurane group (group EI,n =48).30％ fat emulsion and 8％ emulsified isoflurane 0.15 ml/100 g were slowly injected via the tail vein in groups E and EI,respectively.Morris water maze test was performed 6 days before anesthesia.Twelve animals in each group were chosen at 2 h after administration (T1) in E group,at the corresponding time points in C group,or at T1 and 1,7 and 14 days after administration (T2-4) in EI group and underwent spatial probe tests,and the escape latency was measured.The rats were anesthetized with intraperitoneal 1％ pentobarbital sodium 4 g/100 g after the end of Morris water maze test.Blood samples were taken for determination of the plasma S100 protein concentration.The rats were then sacrificed and brains were removed for determination of the expression of hippocampal Aβ and phosphorylated Tau (p-Tau) protein by immunohistochemistry.Results The escape latency and swimming distance were significantly shorter on 3rd,4th and 5th days than those on 1st day of place navigation test before anethesia (P ＜ 0.01).Compared with group C,the escape latency and swimming distance were significantly prolonged and the time of staying at the original platform quadrant was shortened at T1,and the plasma S100 protein concentration was decreased at T4 in group EI (P ＜ 0.05),and no significant change was found in the each parameter of Morris water maze test,plasma S100 protein concentration,and expression of Aβ and p-Tau protein in group E (P ＞ 0.05).The escape latency and swimming distance were significantly shorter and the time of staying at the original platform quadrant was longer at T2-T4 than at T1 in group EI (P ＜ 0.05).Conclusion Emulsified isoflurane anesthesia exerts no effect on the expression of hippocampal Aβ and phosphorylation of Tau protein,indicating that hippocampal Aβ and Tau protein are not involved in emulsified isoflurane anesthesia-induced cognitive dysfunction in rats. Key words: Isoflurane;  Fat emulsions, intravenous;  Amyloid beta-protein;  tau Proteins;  Cognition disorders