The Expression And DNA Methylation Of Mkp-lin The Hippocampus Of Rat Model Of Depression

Objectives1、The establishment of chronic unpredictable stress-induced rat model of depression.2、The detection of the expression of mitogen-activated protein kinase phosphatase-1(MKP-1) and the changes of DNA methylation situation in the promoter of MKP-1gene in the hippocampus of chronic unpredictable stress-induced rat model of depression.3、The affection of antidepressant on the expression of MKP-1and the changes of DNA methylation situation in the promoter of MKP-1gene in the hippocampus of chronic unpredictable stress-induced rat model of depression.Methods1、30SD rats were divided into3groups randomly. They were the control group (A), the saline group (B) and the fluoxetine group (C) respectively. The model was established by chronic unpredictable stress42days. Rats were stimulated by different stress every day, the stress was used at most2times in a week. The model was evaluated by open-field test and weight increment.2、The expression of MKP-1mRNA in the hippocampus was detected by reverse transcription polymerase chain reaction (RT-PCR).3、The methylation of MKP-1:DNA methylation in promoter of MKP-1gene was detected by combined bisulfite restriction analysis(COBRA).4、The data were analyzed by the statistical package for social sciences(SPSS12.0for Windows) and showed as mean±standard deviation(x±s).The data of groups were compared by analysis of variance(ANOVA). The level of a test is0.05. Results 1、Open-field test(1) Horizontal movement:Before the experiment, the differences of distances of the horizontal movement in all groups were not significant statistically (P=0.457). After21days of chronic stimulation, the distances of the horizontal movement of the saline group were further than the distances of the control group (P=0.005), while the differences between the saline group and the fluoxetine group were not significant statistically (P=0.128), the differences between the control group and the fluoxetine group were not significant statistically (P=0.148). After21days of drug treatment, the distances of the horizontal movement of the saline group were shorter than the distances of the control group (P=0.000), the distances of the horizontal movement of the fluoxetine group were further than the distances of the saline group (P=0.000), the differences between the control group and the fluoxetine group were no significant statistically (P=0.393).(2) Vertical movement: The three times of tests were performed at before stimulation,21days of stimulation and21days of treatment, the differences of vertical movement among the three groups were not significant statistically(P=0.260,0.960,0.697).2、Weight increment: Before stimulation, the differences among the three groups were not significant statistically (P=0.476). After21days of chronic stimulation, the weight increment of the saline group was lighter than the weight increment of the control group (P=0.010), the weight increment of the fluoxetine group was also lighter than the weight increment of the control group (P=0.000), the differences between the weight increment of the saline group and the weight increment of the fluoxetine group were not significant statistically (P=0.109). After21days of intervention, the weight increment of the saline group was lighter than the weight increment of the control group (P=0.000), the weight increment of the fluoxetine group was also lighter than the weight increment of the control group (P=0.000), the weight increment of the fluoxetine group was heavier than the weight increment of the saline group (P=0.020).3、The expression of MKP-1mRNA:The saline group was higher than the control group (P=0.001) and the fluoxetine group(P=0.024) respectively; the differences between the fluoxetine group and the control group in the expression of MKP-1mRNA were not significant statistically (P=0.097).4、DNA methylation in the promoter of MKP-1gene:DNA methylation in promoter of MKP-1gene was not found.Conclusions1、The expression of MKP-1mRNA in rat hippocampus was higher suggest that MKP-1may be involved in the mechanism of depression.2、Fluoxetine could significantly relieve the depression-like behavior,weight loss and the expression of MKP-1mRNA in hippocampus. Those suggest that fluoxetine may affect the expression of MKP-1mRNA and was involved in the mechanism of antidepressant treatment.3、DNA methylation in promoter of MKP-1gene did not exist in hippocampus of chronic unpredictable stress-induced rat model of depression which suggest that DNA methylation in promoter of MKP-1gene may not be involved in the mechanism of depression.