Objective To investigate the effect of propofol anesthesia on electroconvulsive therapy (ECT)-induced hyperphosphorylation of Tau protein in hippocampus in depressed rats.Methods Thirty-two female WYK rats in which the total score was 30-120 after Open-field test,aged 24 weeks,weighing 200-250 g,were randomly divided into 4 groups ( n =8 each):control group (group C),propofol group (group P),ECT group (group E)and propofol + ECT group (group PE).In groups C and E,the animals received intraperitoneal normal saline 5 ml,and in addition the animals received ECT 15 min later in group E.In groups P and PE,the animals received intraperitoneal 100 mg/kg propofol 5 ml,and in addition the animals received ECT 15 min later in group PE.The learning and memory function was assessed by Morris water maze test at 24 h after ECT.The animals were sacririced at 6 h after Morris water maze test and the hippocampal tissues were removed for determination of the expression of phosphorylated Tau protein.Results Compared with group C,the escape latency was significantly prolonged,the swimming time was significantly shortened in groups P,E and PE,the expression of phosphorylated Tau protein in hippocampus was down-regulated in group P,and the expression of phosphorylated Tau protein in hippocampus was up-regulated in group E ( P ＜ 0.05).Compared with group E,the escape latency was significantly shortened,the swimming time was significantly prolonged,and the expression of phosphorylated Tau protein in hippocampus was down-regulated in group PE (P ＜0.05).Conclusion The mechanism by which propofol anesthesia improves cognitive impairment induced by ECT may be related to inhibition of hyperphosphorylation of Tau protein in hippocampus in depressed rats.