| Depression is a common mental illness that is primarily associated with persistent mood dysfunction and is one of the leading causes of disability worldwide.As an important public-health problem,its high burden and disability have a large impact on individuals,families,and societyFirst-line antidepressants,such as serotonin selective reuptake inhibitors(SSRI),have notable shortcomings including limited therapeutic efficacy and significant time lag for treatment response.More importantly,long-term and frequent use of antidepressants elicit many side effects,such as orthostatic hypotension,cardiovascular disease,gastrointestinal bleed,epilepsy,and fracture risks.Studies have found that acupuncture is effective in the treatment of depression by alleviating depressive symptoms in rats who have experienced maternal separation.the antidepressant activity of acupuncture combined with an SSRIs is effective,safe,and well-tolerated and may help to reduce side effects of SSRIs and this combination of treatment appears to produce greater antidepressant effects than pharmacotherapy alone.Since EA has been found to be effective in the treatment of depression,there is a large amount of research on its mechanism of action in depression;however,specific mechanisms have not been fully elucidated.In the present study,we investigated the effects of EA on tPA/BDNF pathway-related molecules in the hippocampus to better understand its mechanisms in the treatment of depression,thereby helping provide a theoretical basis for the clinical application of EAObjectiveUsing a rat model of chronic unpredictable mild stress(CUMS).to investigate the effects of electroacupuncture(EA)on the tissue plasminogen activator(tPA)/brain-derived neurotrophic factor(BDNF)pathway.Methods1.Animal groupingSixty male Sprague-Dawley rats were randomly divided into four groups:normal,model,fluoxetine(fluox).or EA.Sixty male Sprague-Dawley specific-pathogen-free rats were permitted to acclimatize for 1 week before experimental procedures began2.Model interventionOther than those in the normal group,rats were all orphaned and Subjected to chronic unpredictable mild stress(CUMS)for 28 days.A total of seven different stressors were used:4? cold water swimming(5 min),day and night reversal(24 h)food deprivation(24 h),water deprivation(24 h),tail pinching(3 min),damp sawdust(24 h),and restraint(3 h).The stimulation alternated every other day and each stimulus appeared no less than four times.3.Treatment methodsBody weight and behavioral performance were measured before and after CUMS.The EA group received 20 min of EA(2 Hz,2 mA)daily at the Baihui(DU20)and Yintang(EX-HN3)acupoints 1 h after CUMS.The needle tip placed at "Baihui" was towards the hind head and the needle tip placed at "Yintang" pointed to the nasal tip.The two needle handles were separated by a cotto n ball to prevent short circuiting.Finally,the fluox group was intragrastrically administered fluoxetine(2 mg/kg;diluted with saline to 1 ml)1 h after modeling daily4.Test indicato rs and methodsAfter the rats were sacrificed,brains were dissected and processed using hematoxylin and eosin(HE)staining to observe changes in the morphology and quantity of neurons in the hippocampal cornu ammonis 3 area.Western blot and real-time polymerase chain reaction(PCR)demonstrated the effects of EA on the tPA/BDNF pathway-related molecules in the hippocampiResults1.Behavioral changeDepression-like status was evaluated by body weight.SPT and OFT.4 weeks of CUMS procedures caused a significant loss in body weight gain(P<0.01),but EA(P<0.01)or fluoxetine(P<0.01)could reverse this change.The CUMS rats developed lower sucrose preference percentage in the SPT(P<0.01).but EA(P<0.01)or fluoxetine(P<0.01)could reverse this change,In the OFT,scores of horizontal and vertical that the rats crawled in the open field box was significantly different between EA group and model group.CUMS rats developed lower horizontal scores(P<0.01)and vertical scores(P<0.01)activity.Compared with CUMS group,the EA group demonstrated more numbers of horizontal(P<0.01;)and vertical(P<0.01).Meanwhile,fluoxetine increased the scores of horizontal(P<0.01),without effecting the scores of vertical(P>0.05).2.Pathological resultsThe results of the light microscopic observation of the hippocampal CA3 showed that these neurons in the normal group were arranged regularly,the cell layer was rich,the cell membrane and cytoplasmic morphology were intact,and the nucleus was round and large.In the model group,the number of hippocampal neurons was significantly reduced,the structure was disordered,the neuron cells were atrophied,the cell shape was irregular,the cell gap became larger,the nucleolus was not obvious,and some neurons were vacuolated.Compared with the model group,the hippocampal cells in the EA and the fluox groups were more regular,the cells were arranged neatly,and the nucleolus was more clear3.Protein levels of BDNF,TrkB,tPA,proBDNF and p75NTR in hippocampusIn model group,the CUMS significantly decreased BDNF(P<0.01),TrkB(P<0.01)and tPA(P<0.01)protein level in the hippocampus,but EA and fluoxetine could reverse this change(P<0.01.P<0.05;respectively).However.the concentration of proBDNF in the hippocampus of rats in the four groups were not statistically significantly different(P>0.05).Both CUMS and fluoxetine markedly elevated the expression of P75NTR in hippocampus of CUMS rats(P>0.05).4.Concentration of BDNF mRNA and tPA mRN A in hippocampusIn model group,the CUMS significantly decreased BDNF mRNA(P<0.01)and tPA mRNA(P<0.05)level in the hippocampus,but EA and fluoxetine could increased the level of BDNF mRNA(P<0.01),while neither EA nor fluoxetine restored tPA mRNA(P>0.05)expression in the hippocampus.Conclusion1.Behavioral test results showed that the horizontal and vertical scores on the OFT and the SPT in the EA and fluox groups were significantly improved.These results indicated that EA and fluox could significantly mitigate depressive symptoms in rats and significantly improve their autonomy and spatial exploration.Both EA and fluox adequately reduced the level of anhedonia in the depressed rats;however,the EA group demonstrated better improvements than the fluox group.2.The content of BDNF,BDNF mRNA,and tPA in the hippocampi of rats in the EA group was higher than that in model group;however,there was no significant difference in hippocampal proBDNF concentration compared to model group.Therefore,we believe that EA promotes the conversion of proBDNF to BDNF by increasing the content of tPA in hippocampus,which elicits antidepressant effects3.In the EA group,the protein concentrations of BDNF and TrkB in the hippocampus were increased compared to the model group,while the concentrations of proBDNF and p75NTR protein had no statistically significant difference.Based on the results.We found that EA elicits an antidepressant effects by increased the concentrations of BDNF and TrkB to maintain neuronal survivalIn summary.EA may reverse depressive-like behaviors in CUMS,which may be related to the tPA/BDNF pathway in the hippocampus. |
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