小剂量氯胺酮对抑郁大鼠海马Rac1蛋白表达及树突棘密度的影响

Effects of low-dose of ketamine on Rac1 protein expression and dendritic spine density in hippocampus of rats with depression

目的探讨小剂量氯胺酮对抑郁大鼠海马Rac1蛋白表达及树突棘密度的影响。方法选取成年雄性SD大鼠60只,分为5组(n=12):对照组(C组)、抑郁组(D组)、氯胺酮组(DK组)、氯胺酮+NSC23766组(DKN组)和NSC23766组(DN组)。采用慢性不可预见性轻度应激法(CUMS)构建大鼠抑郁模型。C组大鼠不接受CUMS应激,腹腔注射生理盐水8mL/kg;其余4组大鼠CUMS处理完成后,D组大鼠行腹腔注射生理盐水8mL/kg;DK组大鼠腹腔注射氯胺酮10mg/kg;DKN组大鼠腹腔注射NSC237662.5mg/kg,5min后给予氯胺酮10mg/kg;DN组大鼠腹腔注射NSC23766 2.5mg/kg。糖水偏好实验和旷场实验用于行为学测试,Western blot检测海马Rac1、Tiam1、α-chimaerin蛋白表达,GST Pull-Down分析Rac1活性,高尔基染色观察脑片海马树突形态。结果CUMS处理后,与C组相比,D、DK、DKN、DN组大鼠的糖水偏好百分比、水平移动距离和直立次数均明显下降(P<0.05),但4组间差异无统计学意义;氯胺酮处理后,与D组相比,DK组糖水偏好百分比、水平移动距离和直立次数明显上升,差异有统计学意义(P<0.05)。与C组相比,D组大鼠海马Rac1蛋白表达下调,活性降低,CA1区树突棘密度下降(P<0.05);与D组相比,DK组大鼠海马Rac1表达上调,活性升高,CA1区树突棘密度增加,差异有统计学意义(P<0.05)。结论小剂量氯胺酮具有良好的抗抑郁效应,其机制可能与上调海马Rac1蛋白表达及活性,继而增加树突棘密度及改善突触可塑性有关。

Objective To investigate the effects of low-dose of ketamine on the expression of Rac1 protein and dendritic spine density in hippocampus of rats with depression. Methods A total of 60 adult male Sprague-Dawley rats were randomly divided into 5 groups (n =12):the control group (group C),the depression group (group D),the ketamine group (group DK),the ketamine+NSC23766 group (group DKN),and the NSC23766 group (group DN).Chronic unpredictable mild stress (CUMS) method was subjected to generate depression models.Rats in group C did not receive CUMS stress but received normal saline (8 mL/kg,i.p.).After CUMS procedure completed in the other four groups,rats in group D were treated with normal saline (8 mL/kg,i.p.).Rats in group DK were treated with ketamine (10 mg/kg,i.p.).Rats in group DKN received NSC23766 (2.5 mg/kg,i.p.),and ketamine (10 mg/kg,i.p.) after 5 minutes.Rats in group DN received NSC23766 (2.5 mg/kg,i.p.).The sucrose preference test and open field test were used to assess behavioral changes.Western blot was used to detect the expression of Rac1,Tiam1 and α-chimaerin in hippocampus.GST Pull-Down was used to analyze the activity of Rac1,and Golgi staining was used to observe the dendrites morphology in hippocampus. Results After CUMS treatment,the percentage of sucrose preference,distance traveled horizontally,and number of vertical in group D,DK,DKN and DN were significantly lower than those in group C (P<0.05),but there was no statistical difference among the four groups.After ketamine treatment,compared with group D,the percentage of sucrose preference,distance traveled horizontally,and number of vertical in DK group increased significantly,the difference was statistically significant (P<0.05).Compared with group C,the expression of Rac1 protein in hippocampus was down-regulated,the activity of Rac1 protein decreased,and the dendritic spine density in CA1 region decreased in group D (P<0.05).Compared with group D,the expression of Rac1 in hippocampus was up-regulated,the activity of Rac1 increased,and the density of dendritic spine in CA1 area increased in group DK,the difference was statistically significant (P < 0.05 ). Conclusion Low-dose of ketamine has a good antidepressant effect,which may be related to up-regulation of hippocampal Rac1 protein expression and activity,and in turn increases dendritic spine density and improves synaptic plasticity.