Abstract: Objective To investigate the effects of taurine on hippocampus mitochondrial ultrastracture changes and oxidative damage induced by MnCl₂.4H₂O.Methods Eighty Wistar rats were divided randomly into 4 groups:control group,MnCl₂.4H₂O-treatment group,taurine-treatment group,and taurine-prevention group.Hippocampus mitochondria was isolated and prepared for electroscopic scanning and reactive oxygen species(ROS) detection.Hippocampus mitochondria from healthy rats was also separated and incubated with MnCl₂.4H₂O and taurine in vitro for determination of ROS.Results The dissolve of mitochondrial membrane and cristae and the degeneration of mitochondrial vacuolar were observed in MnCl₂ group.Both taurine treatment and prevention could improve mitochondrial ultrastracture damage induced by MnCl₂.ROS in MnCl 2 group(170.3±6.1) was significantly lower than that of in the control(182.2±5.5) and taurine-prenvention group(207.0±6.0) (t=3.63,P< 0.05; t=11.61,P< 0.05).While ROS in taurine treatment(150.2±3.8) group was the lowest and was different from that of MnCl₂ administration(t=6.31,P< 0.05).In vitro,compared with that of the control(650.7±12.0),ROS was significantly higher in MnCl₂ treatment group(2139.2±24.9,t=137.23; P< 0.05).Taurine-prevention(1734.5±20.7) and taurine-treatment (1477.3±14.8) could markedly down-regulrate ROS (t=37.31,P< 0.05; t=61.01,P< 0.05).Conclusion MnCl₂ treatment could induce ultrastracture morphologic damage of hippocampns mitochonhria in vivo and taurine-prevention and taurine-treaement could evidently down-regulrate the ROS induced by MnCl₂.