| BackgroundAlthough repetitive transcranial magnetic stimulation(repetitive transcranial magnetic stimulition,rTMS)has been widely used in the treatment of depression,the exact mechanisms responsible for its beneficial effects remain unknown.The neuroendocrine dysfunction of hypothalamus-pituitary-adrenal(HPA)axis and related receptor has a close relationship with the development of depression.Some scholars thought that the antidepressant mechanism of rTMS might be related to changes of the neuroendocrine levels of HPA system.Therefore,through observe change of HPA axis levels in the plasma and the expression levels of glucocorticoid receptor(GR)expression in the hippocampus,as well as the behavior changes of chronic depression model rats,we try to explore the effect of rTMS on HPA axis in chronic depression model rats and its possible mechanism.Objectives1.To test the mRNA expression of corticotrophin releasing hormone(CRH)in the hypothalamus,and the quantities of adrenocorticotropic hormone(ACTH)and cortic-osterone(CORT)in the rats’ plasma,thereby investigating the influence on the HPA levels of rat models from the rTMS.2.To investigate the expression levels of GR in the hippocampus of all rats and the effect of rTMS intervention on their expression levels.3.To analysis the relationship between changing levels of HPA axis and GR expression of rats subjected to chronic stress depression protocol after rTMS,and explore the possible antidepression mechanism of rTMS.Methods1.After screening,39 male SFP grade Sprague-Dawley rats were randomly divided into a blank control(n=8)or a stress-induced group(n=31).The stress-induced model consisted of singly housing the rats and subjecting them to chronic unpredictable mild stress(CUMS).Evaluating their severity of depression as determined by body weight measurements and performance in the sucrose consumption and open field tests,rats failing to show depression in response to this treatment(N=7)were removed from the study.The remaining 24 CUMS rats were randomly divided into three groups(N= 8/group):1)Depression group: No further treatment,2)rTMS group: rTMS intervention using 10 Hz rTMS and 3)Sham group: Receiving simulations of pseudo rTMS treatments.2.rTMS intervention: Rats in rTMS group were given100%MT rTMS intervention for 10 Hz every day,a total of 10 mins,1000 pulse.A total of 3 courses of rTMS interventions were administered over 5 consecutive days for 1 course,with the interval between each of the 2 courses being 2 days.Rats in sham group were given the same environment but no magnetic pulse.3.Measure the body weight of rats and record their changes;Use the sucrose consumption test to detect the interest,pleasure and reward responsiveness in rats;Use open field test(OFT)to detect the ability of self-exploration and spontaneous movement;Assess the model of depression through the above behavioral data.4.Use enzyme-linked immunosorbent(Elisa)to observe the ACTH and CORT concentrations in the plasma of rats.5.Use the immunohistochemical techniques to detect the expression levels of GR protein in the hippocampus of rats,use reverse transcription polymerase chain reaction(RT-PCR)to detect the expression levels of GR in hippocampus and CRH mRNA in hypothalamus of rats.6.Use independent samples T-test,Nonparametric test and ANOVA to analyze exp-er imental data,multiple comparison use LST test.Inspection level α is 0.05.Results1.Behavioral assessment results:The overall weight distribution in rats to meet the normal distribution,the homogeneity is high;Differences of sucrose consumption(t=0.057,P>0.05),horizontal mov-ement distance(t=0.368,P>0.05),the number of vertical upright(t= ﹣ 0.079,P>0.05),modification times(Z=﹣0.317,P>0.05)and central residence time(Z=﹣1.105,P>0.05)were not statistically among the four groups prior to CUMS.After subjecting rats to the CUMS regimen,compared with the control group,differences of the body weight increase rate(Z= ﹣ 2.612,P<0.05),sucrose consumption(t=3.553,P<0.01),horizontal movement distance(t=5.321,P<0.01),the number of vertical upright(Z=﹣3.484,P<0.01),modification times(t=5.144,P<0.01)and central residence time(t=﹣9.758,P<0.01)in model group were statistically significant,it suggest that depression model is successful.After rTMS intervention,differences of the body weight increase rate(χ~2=9.345,P<0.05),sucrose consumption(F=5.041,P<0.01),horizontal movement distance(Fh=27.106,P<0.01),the number of vertical upright(χ~2=20.928,P<0.01),modification times(Fm=27,P<0.01)and central residence time(χ~2=24.067,P<0.01)in four groups were statistically significant.Compared with the control group,the body weight increase rate,sucrose consumption,the various sports levels of the open field test in depression and sham group were significantly decreased.There’s a significantly difference in these points(P<0.05).Compared with depression and sham group,the body weight increase rate,sucrose consumption and levels of the open field test in rTMS group were significantly increased,the difference was statistically significant(P<0.05).There’s no difference between depression group and sham group(P>0.05).2.Biochemical test results: The concentrations of ACTH(F=96.841,P<0.01)and CORT(F=134.550,P<0.01)in the four groups were statistically significant.Compared with the control group,the ACTH and CORT concentrations in plasma of de-pression and pseudo stimulation group were significant rise,the difference have stati stical significance(P<0.01);Compared with model group and pseudo stimulation,the ACTH and CORT concentrations of rTMS group were significantly reduced,and the difference is statistically signifycant(P<0.01).3.Morphology results: The differences of GR mean density(χ~2CA1=14.784,FCA3=170.833,FDG=274.929,P<0.01)of rats hippocampus in four groups were statistically significant.Compared with the control group,the GR mean density in depression group and sham group were significantly lower.Compared with depression group and sham group,the mean density of GR in rTMS group was higher,the difference was statistically significant(P<0.01).There’s no difference between depression group and sham group(P>0.05).4.Detection of gene expression: The expression levels of GR mRNA in rats hippocampus(F=99.069,P<0.01)and CRH mRNA in the hypothalamus(F=55.823,P<0.01)in four groups was significantly different.Compared with the control group,the expression level of CRH mRNA in depression group and sham group were significantly higher,and the expression level of GR mRNA in the two groups were significantly lower,the difference was statistically significant(P<0.01).Compared with the depression and sham group,the rTMS group’s expression level of CRH mRNA were significantly lower and the expression level of GR mRNA were significantly higher(P<0.01).ConclusionsrTMS intervention could ameliorate the overactive HPA axis and depression behavior of chronic stress depression rats and callback the hippocampus reduced GR expression.And rTMS probably played an important role in HPA axis horizontal regulation by accommodating the expression of GR in the hippocampus,so as to achieve the purpose of improving depressive symptoms,which could be one of the potential mechanisms of the antidepression effect of rTMS. |
PDF Full Text Request