ABSTRACT
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.
ABSTRACT
Objective:To investigate the effect and mechanism of non-selective histone deacetylase (HDAC) inhibitor sodium butyrate (NaB) on neuropathic pain and pain-induced memory impairment in mice.Methods:Forty clean grade male C57BL/6J mice were were divided into 4 groups by random number table method ( n=10 in each group): sham + saline, sham + NaB, chronic constriction injury (CCI)+ saline and CCI + NaB.The mouse CCI model was established by sciatic nerve ligation. Non-selective HDAC inhibitors NaB(300 mg/kg) was intraperitoneally injected into the mice in Sham+ NaB group and CCI+ NaB group once a day 15-28 days after modeling, while the mice in Sham+ saline group and CCI+ saline group were intraperitoneally injected with the same volume of saline. On the 14th and 28th day after operation, the athletic ability was measured by open field test (OFT), the pain behavior was measured by paw withdrawal threshold (PWT) and paw withdrawal latency (PWL), and the memory function was measured by Y-maze. After the behavioral experiment, hippocampus and spinal dorsal horn tissues were taken for the activity of HDAC measurement, and hippocampus tissues were taken for the expression levels of BDNF and PSD95 measurement. SPSS 25.0 software was used for statistical analysis. The data were compared by repeated measurement ANOVA and one-way ANOVA. Results:After treatment with NaB, the interaction effects of the accuracy of spontaneous alternation of PWT, PWL and Y maze in mice were significant( F=21.07, 6.98, 7.79, all P<0.05). Compared with the Sham + saline group, the PWT((0.83±0.30)g, (0.25±0.22)g, (0.24±0.11)g; both P<0.05), the PWL((14.97±4.02)s, (5.99±1.51)s, (6.87±0.90)s; both P<0.05) and the spontaneous alternation in Y maze(71.57±2.80)%, (56.96±0.60)%, (62.86±4.94)%; both P<0.05) in CCI+ Saline group and CCI+ NaB group were lower. After treatment with NaB, compared with CCI + saline group, PWT((0.22±0.13)g, (0.62±0.23)g; P<0.05), PWL((5.62±2.00)s, (8.82±2.13)s; P<0.05)and the accuracy of spontaneous alternation of Y maze were significantly higher ((56.54±7.50)%, (66.35±8.20)%; P<0.05), the HDAC activity in hippocampus((173.40±7.38)%, (122.70±8.40)%; P<0.05)and in spinal cord ((153.40±10.58)%, (111.40±11.40)%; P<0.05)were significantly lower, and the expression of BDNF((0.65±0.06), (0.87±0.43); P<0.05)and PSD95((0.70±0.40), (0.87±0.04); P<0.05)were significantly higher in CCI + NaB group. Conclusion:NaB can improve neuropathic pain and pain-induced memory impairment.The mechanism may be related to the inhibition of HDAC activity and the up-regulation of BDNF and PSD95 expression in hippocampus.