Study Of Ketamine Combined With DHA On Lipopolysaccharide-induced Depression-like Behavior In Rats And Its Mechanism

Depression has become a common clinical mental illness.Recent studies have shown that neuroinflammation is related to depression.The cytokine theory has become the mainstream of depression research.LPS-induced rat depression-like model is widely used,which is a typical animal depression model of cytokine theory.Ketamine is a rapid antidepressant,and it is a popular drug in the study of antidepressants at present.Because of its safety,more effective ways and methods of medication are needed.At present,the clinical application of ketamine and other drugs in combination to achieve a better antidepressant effect,so it is necessary to explore the efficacy of ketamine and other antidepressants combined treatment.DHA is an unsaturated fatty acid,which is often used as an adjunct to antidepressant therapy in clinic.It has a promising application prospect due to its safety and antidepressant effect.The purpose of this study was to investigate the effect of ketamine and DHA on the depression-like behavior of rats induced by lipopolysaccharide and its mechanism,so as to provide a model reference for the clinical efficacy of combined antidepressant therapy.The rats were randomly divided into 6 groups: NC group(control group),LPS group(lipopolysaccharide group),LPS + KET group(lipopolysaccharide + ketamine group),LPS + DHA group(lipopolysaccharide + DHA group),and LPS + KET + L-DHA group(lipopolysaccharide + ketamine + low-dose DHA group),LPS + KET + H-DHA group(lipopolysaccharide + ketamine + high-dose DHA group).DHA was administered to rats for 7 days at a dose of 100 mg/kg and 400 mg/kg DHA.Rats were injected intraperitoneally with 1 mg/kg lipopolysaccharide.Twenty-four hours after lipopolysaccharide injection,rats were injected intraperitoneally with 10 mg/kg of ketamine.Behavioral tests were performed 2 hours after drug action.Behavioral tests were: forced swimming test,sucrose preference test,tail suspension test.Nissl staining was used to detect histopathological changes in the hippocampus.Depression-related factors were detected using immunohistochemistry and ELISA kit Changes of BDNF,IL-1,IL-6,and TNF-? were detected by Western blot.Depression-related proteins p-p65,p-CREB,and BDNF were detected.PC12 cells were selected for in vitro verification,PC12 was observed for cell morphology,p-p65 expression was detected by immunofluorescence experiment,and the changes of the above-mentioned depression-related factors and depression-related proteins were detected by ELISA kit and Western blot.Results:(1)In behavioral experiments,lipopolysaccharide increased the immobility time of forced swimming and tail immobility experiments in rats,and reduced the sucrose consumption percentage in rats.The combined application of ketamine and DHA can reverse these changes,including reducing swimming immobility time and tail immobility time,and increasing sucrose preference in rats.(2)Nissl staining showed that lipopolysaccharide can reduce the number of nerve cells in the dentate gyrus,and the combination of ketamine and DHA can reverse the nerve damage caused by lipopolysaccharide.In the morphological observation of PC12 cells in vitro,the combined application of ketamine and DHA can reverse the damage caused by lipopolysaccharide and make PC12 nerve cell morphology closer to normal cell morphology.(3)Ketamine combined with DHA can significantly reduce the levels of IL-1,IL-6 and TNF-? in the hippocampus and PC12 cells,and increase the level of BDNF.Immunohistochemical results showed that the expression level of BDNF in rat hippocampus was significantly higher in the LPS + KET + H-DHA group than in the lipopolysaccharide group.(4)The immunofluorescence results show that the combination of ketamine and DHA can effectively inhibit the nuclear transport of p-p65 and effectively inhibit the occurrence of inflammation.Western blot results show that ketamine combined with DHA can effectively inhibit the expression of depression-related protein NF-k B in hippocampus and PC12 cells,and increase the expression of P-CREB and BDNF.