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Objective:To evaluate the relationship between the mechanism underlying the antidepressant effect of S-ketamine and hippocampal gamma-aminobutyric acid B receptor (GABA BR) in mice. Methods:A total of 54 male C57BL/6(B6) mice, aged 8 weeks, weighing 25-30 g, were used in this study. Forty mice were selected to develop the depression model by chronic social defeat stress. Twenty-six depression-susceptible mice were screened out by social avoidance test at day 11 after developing the model and divided into 2 groups ( n=13 each) by a random number table method: depression-susceptible group (Sus group) and depression-susceptible + S-ketamine group (Sus + S-ket group). The remaining 14 mice served as control group (C group). Starting from day 12 after developing the model, S-ketamine 10 mg/kg was intraperitoneally injected every day for 3 consecutive days in Sus+ S-ket group, while the equal volume of normal saline was given instead in C group and Sus group. The open field test was performed at 1 h after the last administration, and the total distance of movement was recorded. The forced swimming test was performed at 1 day after the open field test, and the immobile time was recorded. The sucrose preference test was performed to calculate the proportion of sucrose consumption at 1 day after the forced swimming test. One hour after the end of behavioral test, mice were sacrificed, and the hippocampal tissues were removed. Western blot was used to detect the expression of GABA BR1, GABA BR2, mammalian target of rapamycin (mTOR), phosphorylated mTOR (p-mTOR), brain-derived neurotrophic factor (BDNF), tyrosine kinase receptor B (TrkB), phosphorylated TrkB (p-TrkB), glutamate receptor 1 (GluR1) and postsynaptic dense protein 95 (PSD95). The p-mTOR/mTOR ratio and p-TrkB/TrkB ratio were calculated. The fluorescence intensity of BDNF in hippocampal CA1 region was detected by immunofluorescence. The number of dendritic spines in hippocampal CA1 region was measured by Golgi staining. Results:In the open field test, no statistically significant difference in the total distance was detected among the three groups ( P>0.05). Compared with C group, the immobile time in the forced swimming test was significantly prolonged, the proportion of sucrose consumption was decreased, the expression of hippocampal GABA BR1, GABA BR2, BDNF, GluR1 and PSD95 was down-regulated, and the ratios of p-mTOR/mTOR and p-TrkB/TrkB were decreased, the fluorescence intensity of BDNF and total number of dendritic spines in the hippocampal CA1 region were decreased in Sus group ( P<0.05), and no significant change was found in the parameters mentioned above in Sus+ S-ket group ( P>0.05). Compared with Sus group, the immobile time in the forced swimming test was significantly shortened, the proportion of sucrose consumption was increased, the expression of hippocampal GABA BR1, GABA BR2, BDNF, GluR1 and PSD95 was up-regulated, the ratios of p-mTOR/mTOR and p-TrkB/TrkB were increased, and the fluorescence intensity of BDNF and total number of dendritic spines in the hippocampal CA1 region were increased in Sus+ S-ket group ( P<0.05). Conclusions:The mechanism underlying the antidepressant effect of S-ketamine may be related to up-regulation of hippocampal GABA BR expression, activation of mTOR-BDNF signaling pathway, and improvement in synaptic plasticity in mice.
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Objective To observe the effect of enriched environment (EE) on the pain threshold and depression like behavior in mice with chronic constriction injury (CCI) and the underly ing mechanism.Methods Sixty C57/BL6 mice were equally randomized into five groups:sham operation group (group Sham),CCI+standard environment(SE) group (group CS),CCI+EE group (group CE),CCI+EE+temozolomide group (group CET),CCI+EE+lipopolysaccharide group (group CEL).The paw withdraw threshold (PWT),paw withdraw latency,forced swim test (FST)and sucrose preference test (SPT) were evaluated,after the operation,meanwhile the hippocampal bromodeoxyuridine (Brdu),ki67 and doublecortin (ICX) positive cells,tumor necrosis factor-α (TNF-α) and interleukin-1β(IL-1β) were determined.Results Compared with group Sham,the PWT,PWL,sucrose consumption and Brdu,Ki67,DCX positive cells were significantly decreased,the immobility time and levels of TNF-α and IL-1β were obviously increased in group CS (P＜0.05).Compared with group CE,the PWT,PWL,sucrose consumption and Brdu,Ki67,DCX positive cells were significantly decreased in groups CS and CEL.The immobility time was obviously increased in groups CS,CET and CEL,moreover,the levels of TNF-α and IL-1β were significantly increased in groups CS and CEL (P＜0.05).Conclusion EE can improve the neuropathic pain,depression-like behavior and neural regeneration in mice with CCI.The inhibition of neural regeneration can block EE-induced improvement of depression-like behavior,but does not affect the pain threshold in mice with CCI.The augmentation of central inflammation can attenuate EE-induced improvement of pain threshold and depression-like behavior in mice with CCI.
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Objective To investigate the role of histone lysine methyltransferase G9a in sevoflurane-induced cognitive impairment in the developing brain of neonatal rats.Methods Thirty-six 5-day-old male SD rats were randomly divided into 3 groups (n =12):control group,sevoflurane group and Bix01294 (the inhibitor of histone lysine methyltransferase G9a)group.The rats in the sevoflurane group and the Bix01294 group received 3% sevoflurane anesthesia for 2 hours once a day at postnatal 5-7 days (P5-P7 ).The rats in the Bix01294 group received Bix01294 (10 mg/kg)subcu-taneously at 1 5 min before anesthesia,and the rats in the control group and sevoflurane group received normal saline for injection (0.1 ml)at the same time.The open-field test and fear condition-ing test were performed at P3 5 and P3 9-P41 ,respectively.The tissues of hippocampus were collected at P42 to measure the levels of G9a,histone H3 lysine 9 dimethylation (H3K9me 2 )and synapsin 1. Results Compared with the control group,the percentage of freezing time of sevoflurane group was significantly decreased in the contextual fear condition test,while the levels of G9a and H3K9me 2 were significantly increased and the level of synapsin 1 was significantly decreased (P <0.01).How-ever,the percentage of freezing time of Bix01294 group was significantly increased,while the levels of G9a and H3K9me 2 were significantly decreased and the level of synapsin 1 was significantly in-creased compared with the sevoflurane group (P <0.05).There was no difference in the total distance and residence time in the central grid in the open-field test,and the percentage of freezing time in the cued fear condition test among the three groups.Conclusion Histone lysine methyltransferase G9a is involved in the sevoflurane-induced long-term cognitive impairment in developing brain of neonatal rats,which may be associated with the increase of H3K9me 2 and the down-regulation of synapsin 1 in the hippocampus.
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Objective To observe the effects of enriched environment on cognitive function in mice with sepsis-associated encephalopathy and to study the neuron PAS domain protein 4 (NPAS4)/brain deprive neurotrophic factor (BDNF)related mechanisms.Methods Sixty adult male mice were divided randomly into three groups:sham operation with standard environment group (group SS,n =12),cecal ligation and puncture with standard environment group (group CS,n =24),cecal ligation and puncture with enriched environment group (group CE,n =24).All mice were reared in standard environment or enriched environment for 28 days.The fear condition test was conducted on day 29 af-ter operation in mice.The change of NPAS4 and BDNF,the density of dendritic spine were detected by western blot or golgi staining.Results Compared with group SS,the context freezing time, NPAS4 and BDNF expression and the density of dendritic spine in hippocampus decreased significantly in group CS (P < 0.05).Compared with group CS,the context freezing time,NPAS4 and BDNF expression and the density of dendritic spine in hippocampus increased significantly in group CE (P <0.05).No significant difference was observed in the conditional freezing time among three groups.Conclusion Enriched environment can obviously improve cognitive function impairment induced by sepsis-associated encephalopathy,which may be related with up-regulated expression of NPAS4/BDNF,and promoted synaptic plasticity.