褪黑素对慢性不可预知温和刺激大鼠抑郁样行为的影响

Effects of melatonin on depression-like behavior in rats with chronic unpredictable mild stimulation

目的研究褪黑素(MT)对慢性不可预知温和刺激(CUMS)大鼠抑郁样行为的影响及相关机制。方法将100只SD大鼠随机分为空白组、模型组、对照组及实验组,各25只。模型组、实验组及对照组大鼠均用CUMS方法建立大鼠抑郁模型。造模成功后,实验组及对照组大鼠分别腹腔注射褪黑素10 mg·kg^-1·d^-1和氟西汀10 mg·kg^-1·d^-1,空白组与模型组则腹腔注射等量生理盐水。各组均连续干预21 d。用糖水偏爱实验、旷场实验、强迫游泳实验观察大鼠抑郁样行为的变化;以苏木精-伊红(HE)染色法观察大鼠海马组织病理学变化;用化学比色法检测海马组织丙二醛(MDA)、活性氧(ROS)、过氧化氢酶(CAT)及超氧化物歧化酶(SOD)水平;用蛋白质印迹(Wb)法检测各组大鼠海马组织鸟嘌呤核苷酸偶联蛋白(GIα)、蛋白激酶C(PKC)及三磷酸肌醇(IP3)蛋白表达水平。结果空白组、模型组、实验组及对照组大鼠水平运动次数分别为(89.67±11.43),(32.49±4.68),(68.42±9.56),(80.15±10.32)次;垂直运动次数分别为(17.45±2.31),(5.87±1.54),(9.75±2.01),(12.46±1.73)次;糖水偏好百分比分别为(84.25±17.36)%,(48.71±11.43)%,(65.12±13.04)%,(73.46±15.63)%;游泳不动时间分别为(91.52±40.63),(148.17±27.34),(131.22±21.07),(114.64±34.36)s。与空白组相比,模型组、实验组及对照组大鼠水平运动次数、垂直运动次数、糖水偏好百分比及海马组织CAT及SOD水平显著降低,且实验组及对照组高于模型组,对照组高于实验组;游泳不动时间、海马组织MDA、ROS水平及GIα、PKC及IP3蛋白相对表达量显著升高,且实验组及对照组低于模型组,对照组低于实验组(均P<0.05)。结论褪黑素可减轻CUMS大鼠海马组织的氧化应激损伤,同时改善其抑郁样行为,其作用机制可能与抑制海马组织PKC-IP3信号通路的信号转导有关。

Objective To investigate the effects of melatonin(MT)on depression-like behavior in rats with chronic unpredictable mild stimulation(CUMS)and its related mechanisms.Methods A total of 100 SD rats were randomly divided into blank group,model group,control group and test group,25 rats in each group.Rats in model group,test group and control group were all established with the CUMS method.After successful modeling,test group and control group were injected intraperitoneally with MT(10 mg·kg^-1·d^-1)and fluoxetine(10 mg·kg^-1·d^-1),blank group and model group were intraperitoneally injected with the same amount of normal saline for 21 d.The changes of depression-like behavior in rats were observed by sucrose preference experiment,open field experiment and forced swimming experiment;histopathological changes in hippocampus of rats were observed by hematoxylin-eosin(HE)staining;the levels of malondialdehyde(MDA),reactive oxygen species(ROS),catalase(CAT)and superoxide dismutase(SOD)in hippocampus were detected by chemical colorimetry method;Western blotting(Wb)method was used to detect the expression levels of guanine nucleotide-coupling protein(GIα),protein kinase C(PKC)and inositol triphosphate(IP3)protein in hippocampus of each group.Results The number of horizontal movements of blank group,model group,test group and control group were(89.67±11.43),(32.49±4.68),(68.42±9.56)and(80.15±10.32)times;the number of vertical movements were(17.45±2.31),(5.87±1.54),(9.75±2.01)and(12.46±1.73)times;the sugar water preference percentage were(84.25±17.36)%,(48.71±11.43)%,(65.12±13.04)%,(73.46±15.63)%;the swimming still time were(91.52±40.63),(148.17±27.34),(131.22±21.07),(114.64±34.36)s.Compared with blank group,the number of horizontal movements,the number of vertical movements,the sugar water preference percentage,the levels of CAT and SOD in hippocampus were significantly reduced in model group,test group and control group,test group and control group were higher than model group,and control group were higher than test group;the swimming still time,the levels of MDA and ROS in hippocampus,the relative expression of GIα,PKC and IP3 protein were all significantly increased,test group and control group were lower than model group,control group were lower than test group(all P<0.05).Conclusion MT can alleviate oxidative stress damage in hippocampus of CUMS rats and improve their depression-like behavior.The mechanism may be related to the inhibition of PKC-IP3 signaling pathway in hippocampus.