| ObjectiveIn this study,the therapeutic effect and possible mechanismsinvolved in electroacupuncture(EA)stimulation were carried out using anacute depression mouse model which was induced by respine injection.The purpose of this study is to elucidate the antidepressant effect of EA stimulation on promoting neurogenesis for depression treatment through activating the BDNF/TrkB signaling pathway in the brain.The study provides a new direction for the mechanism exploration of EA stimulation as a traditional therapy for depression treatment,and provides ideas and theoretical basis for clinical treatment.Methods1.A rat model of acute depression was established byreserpine injection(4 mg/kg,3 d)intraperitoneally(i.p.).Tailsuspension test,forced swimming test and open-field test were carried out to observe whether the acute depression model was established successfully.EA stimulation was performed lasting for 7 d to evaluate whether the EA stimulation could ameliorate depression-like behaviors of reserpine-insulted rat(reserpine was injected after EA pretreatment for 3 d,and behavioral tests were conducted 30 min later after EA stimulation).Fluoxetine-treated group(FLXT,20 mg/kg,3 d)was usedas positive control,and saline administration served as negative control.2.The proliferation of neural stem cell(NSC)in dentate gyrus(DG)of hippocampuswas observedusing 5-bromodeoxyuridine(5-bromodeoxyuridine,BrdU,mg/kg 100 i.p.,3 d)incorporation method,The proliferative effect of NSC in DG was compared in depressive rats with or without EA treatment.3.The expression levels of BDNF,TrkB,p-ERK and p-CREB related to BDNF/TrkB signaling pathway in hippocampus from each group were detected by Western blot,and the effects of EA treatment on the expression of proteins in RESP-insulted rats were analyzed.In order to further explorethe antidepressant effectof EA was through BDNF/TrkB pathway,TrkB receptor antagonist GNF5837(1 μg/μL,4 μL/side)was injected into ventriclesof RESP rats stereotactically.Then,the effect of GNF5837 on the expression levels of downstream proteins related to BDNF/TrkB pathway which were affected after EA stimulation was observed.4.To explore whether BDNF/TrkB signaling pathway is involved in EA antidepressant through affecting NSC proliferation,the effect of GNF5837 on EAmediatedNSC proliferation was analyzed after BrdU incorporation,meanwhile,the effect of GNF5837 on depression-like behaviors of RESP-insulted rats was evaluated.Results1.Behavioral results showed thatcompared with the control group,RESP group showed depression-like behaviors characterized as increased immobility time,as well as decreased latency of the immobility in tail suspension test and forced swimming test,indicating the acute depression model was established successfully.Compared with model group,the immobility time was significantly decreased after EA stimulation,indicating that EA amelioratedthe depression-like behaviors of RESP group.Open-field test was used to determinerat spontaneous activities,the data showed that total distance and the time spent in the central area significantly decreased in the RESP group compared with the control group.Compared with the RESP group,the total distance and the time spent in the central area increased in EA+RESP group;Similar results were observed in FLXT group which served as positive control,and there was no significant difference between the FLXT group and EA+RESP group.All the data collected showed that EA treatment improved the activity of depressive rats.2.The proliferation of NSC was measured by BrdU incorporation,and the results showed thatthe number of BrdU-positive NSC decreased significantly in DG of RESP group compared with group control,indicating that NSC proliferation was damaged in RESP group;Compared with the RESP group,the proliferation of NSC in the DG of EA+RESP group increased significantly after EA treatment,and FLXT group had similar results.There was no significant difference between the EA+RESP group and the FLXT+RESP positive control.The results suggested that EA promoted the proliferation of NSC.3.Western blot results showed that the expression levels of BDNF,TrkB,p-ERK and p-CREB significantly decreased in RESP group compared with the control group;Compared with RESP group,the proteins expression increased in EA+RESP group after EA stimulation.GNF5837 pretreatment(injection into the ventricle)abolished the enhanced-expression of p-ERK and p-CREB mediated by EA,suggesting that GNF5837 inhibited the antidepressant effect of EA.There was no difference in the expression levels of p-ERK and p-CREB in hippocampus from GNF5837+RESP group and RESP group.The results showed that GNF5837 blocked the increased expression of proteins related to BDNF/TrkB pathway by EA.4.The results of behavioral test showed that GNF5837 cancelled the decreased immobility time mediated by EA treatment in the TST and FST compared with the EA+RESP group,indicating that GNF5837 abolished the antidepressant effect of EA.5.BrdU incorporation was used to further analyze the effect of GNF5837 on enhanced NSC proliferation induced by EA.The results showed that,compared with the EA+RESP group,GNF5837 pretreatment abolished the proliferative effect of EA therapy,suggesting that GNF5837 antagonized the proliferative effects of EA treatment.ConclusionThis study indicated that the rat model of acute depression was successfully established by i.p injection of RESP,and EA treatment ameliorated the depressivebehaviors of RESP rats.Further mechanism study found that EA exerted antidepressant by improving the injuried NSC proliferation in acute depressive rats by activating BDNF/TrkB signaling pathway.Therefore,promoted NSC proliferation may play an important role in EA antidepressant through BDNF/TrkB signaling pathway in acute depressive rats. |
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