The Antidepressant-like Effect And Mechanisms Of GABA-mediated Anesthetics On Chronic Unpredictable Stress Mice

Background:Depression is a psychological disease characterized by persistent low mood.The current treatment of depression is mainly drug therapy,electroconvulsive therapy and deep brain stimulation are for severe cases.However,current antidepressants have the drawbacks of long onset time,poor efficacy and severe adverse reactions.Electroconvulsive therapy could cause memory impairment or cognitive impairment,while deep brain stimulation requires brain surgery.So it is urgent to find effective antidepressants with low side effect.Many literature reports have shown that ketamine have rapid and long-lasting antidepressant like effect in patients with treatment-resistant depression,these findings has drawn attention to the use of anesthetics in antidepressant treatment.The latest studies have found that propofol or midazolam,as commonly used anesthetics in clinical practice,can improve depression-like behaviors in depressed animals.However,there are few studies have been reported about the mechanism by which propofol or midazolam regulate depression-like behaviors.Based on the above information,this study mainly investigated the improvement effect of propofol or midazolam on depression-like behaviors and theirs potential regulatory mechanisms.Methods:In this study,we first explored the effect and possible mechanisms of propofol or midazolam on depression-like behaviors by chronic unpredictable stress(CUS).To investigate the effect of propofol on depression-like behaviors in CUS mice,male ICR mice were randomly divided into control group,CUS group,CUS+propofol low,medium and high dose groups and CUS+fluoxetine positive group.To investigate the effect of midazolam on depression-like behaviors in CUS mice,male ICR mice were randomly divided into control group,CUS group,CUS+midazolam low,medium and high dose groups and CUS+fluoxetine positive group.Except the control group,mice in other groups were subjected to chronic unpredictable stress for 14 days.On the 15th day,after one hour of single administration,open field test,forced swimming test and tail suspension test were used to investigate the effect of propofol or midazolam on depression-like behaviors in CUS mice;the expression levels of GAD65,GAD67,VGAT,GAT-3 and GABA_AR in the prefrontal cortex and hippocampus of mice were detected by western blot.Then based on the regulatory role of GABA_AR in depression,and propofol or midazolam belong to the GABA_AR agonist anesthetics,so further explored whether blocking GABA_AR with bicuculline had any effect on the antidepressant-like effect of propofol or midazolam.To investigate the effect of bicuculline on the antidepressant-like effect of propofol,male ICR mice were randomly divided into control group,CUS group,CUS+propofol group,CUS+propofol+bicuculline group and CUS+bicuculline group.To investigate the effect of bicuculline on the antidepressant-like effect of midazolam,male ICR mice were randomly divided into control group,CUS group,CUS+midazolam group,CUS+midazolam+bicuculline group and CUS+bicuculline group.Except the control group,other groups mice were subjected to chronic unpredictable stress for 14 days.On the 15th day,bicuculline was given 30 minutes before intraperitoneal injection of propofol or midazolam.Other groups were intraperitoneally injected with the same dose of saline.After one hour,the depression-like behaviors of mice was explored by open field test,forced swimming test and tail suspension test.Western blot was used to detect the expression levels of GAD65,GAD67,VGAT,GAT-3 and GABA_AR in the prefrontal cortex and hippocampus.Immunofluorescence staining was used to investigate the changes of GluA1 expression in hippocampus CA3 subregions and prefrontal cortex.Results:1.The results of the study on antidepressant-like effect of propofol or midazolam showed that the spontaneous activity of CUS mice was not affected,but the immobility time in the forced swimming test and tail suspension test was significantly shortened by the administration of medium dose of propofol or low dose of midazolam.In western blot,the decrease of GAD65,GAD67,VGAT,GAT-3 and GABA_AR levels in the hippocampus of mice induced by CUS were most significantly reversed by the medium dose of propofol or low dose of midazolam.In the prefrontal cortex,the decrease of GAD65 and GABA_AR levels of mice induced by CUS were most significantly reversed by the medium dose of propofol,the decrease of GAD65,GAD67,VGAT and GABA_AR levels of mice induced by CUS were most significantly reversed by the low dose of midazolam.2.The results of study on the effect of bicuculline on the antidepressant-like effect of propofol and midazolam showed that the improvement effect of propofol or midazolam on the immobility time in the forced swimming and tail suspension were significantly antagonized by bicuculline.In western blot,compared with the propofol group,the improvement of GAD65,GAD67,VGAT,GAT-3 and GABA_AR levels in the hippocampus and GAD65 and GABA_AR levels in the prefrontal cortex were significantly antagonized by bicuculline.Compared with the midazolam group,improvement of GAD65,GAD67,VGAT,GAT-3 and GABA_AR levels in the hippocampus and GAD65,GAD67,VGAT and GABA_AR levels in the prefrontal cortex were significantly antagonized by bicuculline.Finally,immunofluorescence staining results showed that the expression of GluA1 in the CA3 subregions of the hippocampus was significantly down-regulated in the CUS group compared with the control group,which was restored by propofol or midazolam.However,the ameliorating effect induced by propofol or midazolam was antagonized by bicuculline.In the prefrontal cortex,the GluA1expression level was significantly down-regulated in the CUS group compared with the control group,which was restored by midazolam.However,the ameliorating effect induced by midazolam was antagonized by bicuculline.Conclusion:In summary,middle dose of propofol or low dose of midazolam have significant improved depression-like behaviors of mice induced by CUS,effectively increased the expression of GABA synthases and transporters.Moreover,the antidepressant-like effect of propofol or midazolam can be antagonized by GABA_AR antagonists.This study highlights the importance of GABAergic in depression and provides a theoretical basis for antidepressant research with propofol or midazolam.