Objective To investigate the effect of oxytocin on the expression of MKP-1 level in the hippocampus of post-traumatic stress disorder rats.Methods Eighteen SD rats were randomly divided into the control group,administration group and the experimental group with 6 rats in each group.The administration group and the experimental group were treated with internationally recognized single prolongation stress (SPS) method to stimulate the rats in order to establish PTSD models.The 14-day oxytocin intervention was given to rats of the administration group after the SPS stimulation within 8 hours.And the behavioral changes of rats were observed by open-field test and Morris water maze test.The changes of MKP-1 mRNA in the hippocampus of rats were detected by real-time quantitative PCR (qRT-PCR),and the levels of MKP-1 Protein in the hippocampus of rats were detected by Western Blot.Results (1) Compared with the model group (2.50± 1.05 and 22.16±7.14),the times of the standing and crossing grid section quantities in the open-field test in the administration group(5.16± 1.17and 32.83±5.71) and control group (6.67±2.16 and 39.83± 4.62) significantly decreased (P＜0.05).Morris water maze showed that the incubation of the model group was markedly prolonged (P＜0.05) compared with that of the administration group,while in spatial probe test,the incubation period of the rats in administration group was prolonged,and the number of wearing stage decreased (P＜0.05).(2) Compared with the administration group (1.30±0.03),the expression of MKP-1 mRNA in hippocampus of rats in model group (4.04±0.46) was notably up-regulated (P＜0.05).And the protein level of MKP-1 in model group(1.95±0.68) was also increased compared with that in administration group (1.46±0.27) (P＜0.05).Conclusions Oxytocin can protect the learning and memory ability and reduce the stress-related performance of rats via regulating the expression of MKP-1.