| Objective: To explore the preliminary anti-depression mechanism of S-ketamine in prenatally stressed offspring,particularly around neuroplasticity.Methods: Female mice were mated with male mice overnight at a ratio of 2:1 and the day of vaginal plug detection was defined as the gestational day(GD)1.The pregnant females were randomly divided into two groups,the control group did not undergo any stress during pregnancy,and the prenatal stress(PNS)group was given chronic unpredictable mild stress on the 7th-20 th day of pregnancy.The offspring were weaned on postnatal day(PND)21 and were intraperitoneally injected with S-ketamine or saline on postnatal day(PND)42.The offspring groups were based on a combination of PNS paradigm and drug treatment and are as follows: Control+Saline,Control+S-ketamine,PNS+Saline,PNS+S-ketamine.One hour after injection,we assessed depressive-like behavior through a series of behavioral tests(Open field test,OFT;Forced swim test,FST;Tail suspension test,TST;Sucrose preference test,SPT).To elucidate the mechanism by which S-ketamine improves depression,the dendritic complexity,we observed hippocampal neuropathological changes in offspring by Nissl staining.Dendritic spine density and synaptic ultra-microstructure of hippocampal CA1 pyramidal neurons were observed by Golgi-cox staining and transmission electron microscopy.Furthermore,protein levels of BDNF/AKT/m TOR signaling pathway and synaptic plasticity-related proteins(PSD95,Synaptophysin)were assessed by Western blot(WB).The m RNA level of BDNF,PSD95 and Synaptophysin were analyzed by real-time fluorescence based quantitative PCR(RT-PCR).Results: Behavioral results showed that: In the OFT,no significant difference in total traveled distance within 5?min was observed among the four groups(P > 0.05).Compared with the Control+Saline group,the PNS+Saline group showed prolonged immobility in the FST and TST(P < 0.01,P < 0.001,respectively)and decreased sucrose preference in the SPT(P < 0.01).S-ketamine significantly attenuated the increased immobility time in the FST and TST(P < 0.01)and ameliorated the decreased sucrose preference in the SPT(P < 0.05)compared with the PNS+Saline group.Nissl staining showed that: Compared with the Control+Saline group,the PNS+Saline group showed severe neuronal degenerative changes and loss in CA1region(P < 0.001).Compared with the PNS+Saline group,the S-ketamine treatment had obvious protective effect on neuronal damage,and increased the intact pyramidal neurons count in CA1 region(P < 0.01).Golgi Cox staining showed that: Compared with the Control+Saline group,the PNS+Saline group showed a lower density of dendritic spines(P < 0.0001)and a significantly decreased number of dendritic intersections in the circle diameter of 30-100μm(30μm: P < 0.01;40μm: P < 0.01;50μm: P < 0.001;60μm: P < 0.0001;70μm: P < 0.0001;80μm: P < 0.0001;90μm: P <0.001;100μm: P < 0.01);Compared with the PNS+Saline group,treatment with S-ketamine significantly increased the density of dendritic spines(P < 0.01)and the number of intersections between 30 and 80 μm(30μm: P < 0.01;40μm: P < 0.01;50μm: P < 0.001;60μm: P < 0.001;70μm: P < 0.001;80μm: P < 0.01).TEM results showed that: Compared with the Control+Saline group,the thickness of postsynaptic density of the PNS+Saline group was significantly shortened(P < 0.01).Treatment with S-ketamine increased the thickness of postsynaptic density comparing with the PNS+Saline group(P < 0.05).There were no significant differences in the synaptic space among all four groups(P > 0.05).WB results showed that: Compared with the Control+Saline group,the ratios of the p-AKT/AKT and p-m TOR/m TOR in the PNS+Saline group were significantly decreased(P < 0.01).Compared with the PNS+Saline group,treatment with S-ketamine increased the p-AKT/AKT and p-m TOR/m TOR ratios(P < 0.05).In addition,prenatal stress significantly decreased the protein levels of BDNF,PSD95 and Synaptophysin(P < 0.05,P < 0.01,P < 0.01,respectively).Compared with the PNS+Saline group,the BDNF and PSD95 protein expression level were increased in the PNS+S-ketamine group(P < 0.05).However,there is no significant difference in the protein expression of Synaptophysin between the PNS+Saline group and the PNS+S-ketamine group(P > 0.05).RT-PCR results showed that: Compared with the Control+Saline group,the m RNA expression of BDNF,PSD95 and Synaptophysin in the PNS+Saline group were significantly decreased(P < 0.05,P < 0.01,P < 0.05,respectively).S-ketamine significantly elevated the m RNA expression of BDNF and PSD95 comparing with the PNS+Saline group(P < 0.05).However,there is no significant difference in the m RNA expression of Synaptophysin between the PNS+Saline group and the PNS+S-ketamine group(P >0.05).Conclusion: Prenatal stress induced by chronic unpredictable mild stress leads to depressive-like behaviors and hippocampal neuroplasticity impairments in male offspring.A single intraperitoneal injection of S-ketamine can produce antidepressant effects by enhancing neuroplasticity via the BDNF/AKT/m TOR signaling pathway. |
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