Relationship between mechanism underlying antidepressant effect of S-ketamine and hippocampal GABA BR in mice / 中华麻醉学杂志

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.