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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 investigate the role of GABAB1 receptors in spinal dorsal horn neurons in the development of diabetic neuropathic pain (DNP). Methods Sixty pathogen free male SD rats aged 4 weeks weighing 150-170 g were randomly divided into 2 groups ( n = 30 each): control group and DNP group. Diabetes mellitus was induced by single intraperitoneal injection of streptozotocin 50 mg/kg. Blood glucose levels and paw withdrawal threshold to mechanical stimuli were measured at 3, 5 and 7 weeks (T1, T2, T3 ) after IP STZ/NS ( n = 10 each). The animals were sacrificed after PWL measurement. The lumbar segment of the spinal cord was removed for determination of the expression of GABAB1 receptors by immuno-histochemistry, RT-PCR and Western blot analysis. Results The blood glucose levels were significantly higher while the PWT was significantly lower at T1,T2 and T3 in group DNP than in control group. The expression of GABAB1 receptor mRNA and protein in spinal dorsal horn was significantly lower at T2 and T3 in DNP group than in control group. Conclusion The expression of GABAb1 receptors is down-regulated in spinal dorsal horn neurons in rats with DNP.
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Objective To investigate the effects of minocycline,a selective microglia inhibitor on dorsal GABAB receptor expression in the spinal cord in a rat model of neuropathic pain and the possible mechanism.Methods Forty-eight male SD rats weighing 220-260 g were used in this study.Neuropathic pain was induced by ligation of L5 spinal nerve(SNL).The animals were randomly divided into 4 groups(n=12 each):Ⅰ sham operation;Ⅱ SNL;Ⅲ sham operation+intrathecal(IT)minocycline 50 μg;IV SNL+IT minecycline 50 μg.Paw withdrawal threshold to von Frey hair stimulation was measured before operation(baseline)and at post-surgery days 1,2,4,6,8,10,12,14,16,18 in 6 animals in each group.The GABABR2 expression in dorsal horn of spinal cord was detected by Western blot at the time point when paw withdrawal threshold to mechanical stimulation was the lowest in another six animals which did not undergo yon Frey hair stimulation test.Results The paw withdrawal threshold to mechanical stimuli and the GABABR2 expression in the dorsal horn of spinal cord were significantly lower in SNL group than in sham operation group.The decreased paw withdrawal threshold to von Frey hair stimulation and the down-regulated GABABR2 expression in the spinal cord induced by SNL were ameliorated by intrathecal administration of micmglia inhibitor- minocycline in group Ⅳ.Conclusion The mechanism of neuropathic pain mediated by microglia activation may be related to the inhibition of GABAB receptor activation.
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Objectives This study was to evaluate GABA BR (including GABA BR1 and GABA BR2) expression in human gastric cancer. Methods Thirty randomly chosen patients with gastric cancer who underwent surgical treatment were entered into the current study. Immunohistochemistry was carried out to determine the expression of GABA BR. Results Immunohistochemistry analysis showed that the scores of GABA BR1 and GABA BR2 in human gastric cancer tissue increased apparently compared with the adjacent normal tissue(P
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Objective To explore the possible mechanism of GABA B receptor subunit and epileptogenesis in absence seizure animal model Methods AY 9944 absence seizure model is developed by abdomenal injection of a cholesterol biosynthesis inhibitor Ay 9944 to neonatal Lon Evan hooded rats In situ hybridization is applied to detect GABA B receptor subunit GBR1b pan mRNA in rat brain of absence seizure Result There is increased hybridization signal in cortex, hippocampus and thalamus, especially in cortex (361?48 nCi/g) and hippocampus CA1 region (327?83 nCi/g)( P value 0 020 and 0 027 respectively) Conclusion The result of this study support the hypothesis that GABA B receptor subunit may be involved and induce seizures in absence epilepsy The finding of subunit change may direct the screen of new antiepileptic drug This finding deserves further study
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Objective To investigate the effect of GABAB receptor in spinal cord by detecting semi-quantitatively the mRNA for isoforms of GABAB receptor in a chronic neuropathic pain model. Methods Twenty-four male SD rats weighing 200-250g were anesthetized with intraperitoneal pentobarbital. Lamina of L5 vertebra and superior articular process of L6 were removed and posterior root of left L5 spinal nerve was exposed and tightly ligated with 7/0 atraumatic suture. The animals were randomly divided into 4 groups of 6 animals in each group: group A in which animals were observed for 7 days after sham operation; group B in which animals were observed for 7 days after ligation of posterior root of L5 spinal nerve; in group C animals were observed for 14 days after sham operation and in group D animals were observed for 14 days after ligation. Pain threshold was measured by heat stimulation of bilateral hindlimbs before and on the 1st , 3rd , 7th , 10th and 14th day after operation. Lumbar spinal cord was removed on the 7th or 14th day after operation and mRNA for isoforms of GABAB receptor in the spinal cord was detected semi-quantitatively by digoxin hybridization in situ.Results Pain threshold of left hindlimb (ligated side) was significantly lower than that of right hindlimb on the 7th, 10th and 14th day after operation as measured by heat stimulation. There were less mRNA for three isoforms of GABAB receptor in group B and D as compared with group A and C respectively. Conclusion The gene expression of three isoforms of GABAB receptor in the spinal cord has plasticity and is reduced during chronic neuropathic pain.