The Effect And Mechanism Of Venlafaxine On The Exploration And Courtship Behaviors Of Zebrafish (Danio Rerio)

Venlafaxine(VEN)was one of the first clinical drugs for the treatment of human depression.The long-term use of venlafaxine could cause a potentially life-threatening serotonin syndrome.Melatonin(MT)could ameliorate depression behavior.Therefore,the aim of this study was to investigate the antidepressant effects of venlafaxine in combination with melatonin on zebrafish.Reserpine was used to acutely treat zebrafish for 20 minutes to induce depressive behavior,and we explored the antidepressant effect of venlafaxine and melatonin combined treatment for 7 days.We tested the depressive behavior of adult zebrafish through a novel tank test,and evaluated the levels of serotonin(5-HT),dopamine(DA)and noradrenaline(NA)in zebrafish brain using enzyme-linked immunosorbent assay(ELISA),besides that the gene expression of serotonin transporters a(serta),dopamine transporters(dat)and norepinephrine transporters(net),vesicular monoamine transporter2(vmat2)and monoamine oxidase(mao)were evaluated by q RT-PCR.The results showed that,compared with reserpineonly group,venlafaxine(VEN,0.025 mg/L)and melatonin(MT,1 μM)increased the parameters of exploration in the top of the tank and decreased freezing behavior significantly.Compared with reserpine-only group,the use of VEN combined with MT increased serotonin and norepinephrine levels significantly,while there was no obvious difference in dopamine content.The results of q RT-PCR showed that the use of VEN combined with MT significantly reduced the expression of serta and promoted the expression of vmat2,but had no significant effect on the expression of net,dat and mao.The results indicated that venlafaxine combined with melatonin showed more effective role to remedy the depressive symptoms in zebrafish,providing a reference for the clinical application of antidepressants.In addition,it was reported that psychoactive drugs discharged into the environment had different effects on the behavior of vertebrates.The objective of this study was to evaluate the effect of venlafaxine on the behavior of zebrafish,and whether melatonin could reverse the induction of venlafaxine.In this study,a series of venlafaxine concentrations(1μg/L,10 μg/L,100 μg/L)was used to treat zebrafish embryos from 2 hours post-fertilization(hpf)to 5dpf.We found that venlafaxine(1μg/L)could stimulate the growth of the head area,eye area,and body length of zebrafish.The light-dark test showed that venlafaxine(1μg/L)could increase the activity of zebrafish larvae.What’s more,venlafaxine(1μg/L)upregulated the expression of steroid regulatory factors including steroidogenic acute regulatory protein(star),cytochrome P450 family member 11A1(cyp11a1)and 11 β hydroxylase(cyp11b1)by c AMPp CREB pathway,affecting the function of the steroidogenic cells,which might be involved in the increased cortisol levels in zebrafish larvae.Whereas,melatonin(230μg/L)restored the altered locomotion behavior induced by venlafaxine and recovered the altered gene expression.Our results demonstrated that venlafaxine at levels detected in the aquatic environment affected behavior and could compromise the adaptive responses to the environment in zebrafish larvae.Venlafaxine was a widely used antidepressant drug and routinely detected in the aquatic environment.To further evaluate the impact of environmental venlafaxine on zebrafish mating behavior,in this work,adult zebrafish were exposed to environmental concentrations of venlafaxine(1 μg/L,10 μg/L,100 μg/L)for 20 days.Then we observed changes in the mating behavior of female/male zebrafish and their effects on the dopaminergic system.In our study,we evaluated the molecular levels and neuronal basis of that behavior.Here,we showed that venlafaxine inhibited the courtship behavior in zebrafish,and increased transcript levels of 5-ht1 a and 5-ht2 c,while decreased transcript levels of genes involved dopaminergic system,including th1,th2,drd1 b,and drd2 b.Venlafaxine upregulated 5-HT level and downregulated DA level.Moreover,the subordinate fish from the venlafaxine-exposed group had significantly lower motor activity compared to those of the control group.Collectively,our results revealed that environment-related venlafaxine could disturb brain monoamine levels,affecting the courtship behavior in adult zebrafish.