生命早期应激对青春期雄性大鼠下丘脑-垂体-性腺轴的影响

Impact of early-life stress on hypothalamic-pituitary-gonadal axis in adolescent male rats

目的研究生命早期应激对青春期雄性大鼠下丘脑-垂体-性腺轴的影响。方法将SD孕鼠随机分为对照组和模型组,每组4只。对照组孕鼠所产雄性仔鼠(n=28)和模型组孕鼠所产雄性仔鼠(n=26)用于实验。模型组孕鼠产雄性仔鼠出生后第2至9天(PND2~9)给予限制筑窝材料和垫料的应激,对照组孕鼠所产雄性仔鼠正常饲养。PND2至PND21检测两组仔鼠体重和尾长变化。PND21行旷场试验,PND22时部分大鼠腹腔注射水合氯醛麻醉,腹主动脉取血,放射免疫法检测血清皮质酮水平。PND42称量剩余大鼠体重,麻醉取血,解剖并收集大鼠睾丸,称量睾丸湿重并计算睾丸指数,HE染色法观察大鼠睾丸组织结构,放射免疫法检测大鼠血清性激素水平。结果与对照组相比,模型组仔鼠PND2至PND21体重增加和尾长增长均显著减慢(P<0.05);PND21自主活动显著减少[水平运动得分(11.7±7.1)vs.(48.7±11.2),垂直运动得分(0.8±0.5)vs.(5.9±1.7)](P<0.05),修饰持续时间[(19.42±3.47)s vs.(6.79±2.00)s]显著增加(P<0.01),表现出抑郁焦虑状态;PND22的血清皮质酮水平显著下降[(20.00±1.14)ng/ml vs.(23.14±2.46)ng/ml](P<0.001)。PND42模型组大鼠体重、睾丸湿重及睾丸指数均显著低于对照组(P<0.05),显微镜下睾丸组织形态结构发生明显变化,生精小管间连接疏松,间质细胞数量减少;模型组大鼠的血清促性腺激素释放素(GnRH)[(60.99±4.27)vs.(56.40±4.81)pg/ml]和黄体生成素(LH)水平[(6.16±1.71)vs.(4.02±1.90)U/L]显著上升,而雌二醇(E 2)[(29.83±2.78)vs.(39.02±10.60)pmol/L]和睾酮(T)水平[(0.72±0.45)vs.(1.50±0.84)nmol/L]显著下降(P均<0.05)。结论生命早期应激可造成青春期雄性大鼠的生殖系统损伤,并导致下丘脑-垂体-性腺轴的功能失调。

Objective:To study the impact of early-life stress on hypothalamic-pituitary-gonadal(HPG)axis in adolescent male rats.Methods:SD pregnant rats were randomly divided into two groups:the control group(n=4)and the model group(n=4).The male offspring of pregnant rats in the control group(n=28)and the model group(n=26)were used for the experiments.The stress of limited nesting and bedding material was performed during postnatal day 2-9(PND2-9)in male offspring of model group.The male offspring in control group were fed normally.Body weight and tail length were measured from PND2 to PND21.Open-field test was performed to detect the behavioral changes on PND21.Then some of rats were anesthetized with chloral hydrate(350 mg/kg,i.p.)and the blood samples were collected from the abdominal aortas.The content of cortisol in serum was assayed by radioimmunoassay.The body weight was measured and anesthetized to collect the blood samples and testes,and the weight of testis&testicular indexes were determined in the remaining rats on PND42.HE staining was utilized for observing the structure of rat testis tissue.Serum levels of sex hormones were determined by radioimmunoassay.Results:Comparing the control group,the weight gain and tail length growth of offspring from PND2 to PND21 in the model group were significant slowdown(P<0.05).The locomotor activity[horizontal exercise scores(11.7±7.1)vs.(48.7±11.2),upright exercise scores(0.8±0.5)vs.(5.9±1.7)]on PND21 was significantly decreased(P<0.05),the duration of modification[(19.42±3.47)vs.(6.79±2.00)sec.]was significantly increased(P<0.01),and the rats showed depression and anxiety in the model group.The serum cortisol levels[(20.00±1.14)ng/ml vs.(23.14±2.46)ng/ml]on PND22 were significantly reduced in the model group(P<0.001).The body weight,testis weight and testicular indexes on PND42 in the model group were significantly lower than those in the control group(P<0.05).The morphological structure of testicular tissue significantly changed,the number of testicular Leydig cells reduced,and the arrangement of seminiferous tubules was loosened in the model group.Serum levels of GnRH[(60.99±4.27)vs.(56.40±4.81)pg/ml]and LH[(6.16±1.71)vs.(4.02±1.90)U/L]significantly increased(P<0.05),while estradiol(E 2)[(29.83±2.78)vs.(39.02±10.60)pmol/L]and testosterone[(0.72±0.45)vs.(1.50±0.84)nmol/L]significantly decreased in the model group(P<0.05).Conclusions:Early-life stress can be harmful to the reproductive function and induced disorder of HPG axis in male rats.