褪黑素对母婴分离新生鼠行为发育及海马糖皮质激素受体的调节

Effects of melatonin on behavioral development and hippocampal glucocorticoid receptors in rats experienced neonatal maternal separation

目的探讨外源性褪黑素（MT）对母婴分离（MS）新生大鼠行为发育及海马糖皮质激素受体（GR）表达的调节作用。方法按随机数字表法将新生同窝雄性SD大鼠随机分为母婴分离（MS）组、母婴分离＋褪黑素干预（MT）组和对照组，每组12只。MT组和MS组于出生后第1～14天进行母婴分离实验；MT组于出生后第7～20天腹腔注射MT10mg／（kg·d），注射容积10ml／kg，MS组和对照组分别腹腔注射相同容积的生理盐水。于出生后第28天，采用水迷宫试验测试大鼠学习记忆能力；于出生后第30天，取3组大鼠海马组织，采用二步法免疫组织化学染色检测GR阳性细胞表达，采用逆转录聚合酶链式反应法检测GRmRNA表达。结果（1）MS组大鼠水迷宫测试学会正确上台所需的训练次数[（13．3±3．7）次]，较对照组[（8．9±2．1）次]明显增加（P〈0．01），MT组大鼠学会正确上台所需的训练次数[（9．2±2．6）次]，较MT组明显减少（P〈0．01），与对照组比较差异无统计学意义（P〉0．05）；（2）MS组海马GR蛋白（78．56±4．05）及mRNA表达（0．65±0．28）较对照组[（136．04±5．16）、（0．95±0．34）]均明显下降，差异有统计学意义，MT组大鼠海马GR蛋白（129．11±5．03）及mRNA（0．94±0．32）表达明显升高（P〈0．05），与对照组比较差异无统计学意义（P〉0．05）。结论外源性MT可能通过上调海马GR水平减轻早期母婴分离对远期行为发育的损伤。

Objective To explore the effects of melatonin on behavioral development and hippocampal glucocorticoid receptors in rats with experienced neonatal maternal separation. Method Rat pups were randomly divided into maternal separation with melatonin group （MT group） , maternal separation with normal saline group （ MS group） and the control group. Rat pups were separated from their mothers and socially isolated from postnatal days one to 14. The rats in MT group were given melatonin110 mg/（kg · d） , i. p. ] for 14 days from postnatal days 7 to 20. Water maze test was performed to assess learning and memory on days 28 to 29. The sections of hippocampus were obtained on days 30, then immtmohistochemical staining and reverse transeriptase polymerase chain reaction （RT-PCR） was employed to detect the expression of glucocorticoid receptors （GR） gene in hippocampus. Results Compared with the control group [ （8.9 ± 2. 1） times], rats in the MS group [ （13.3 ±3.7） times] had significantly more times in leaning to get to the security area in the water maze test （P 〈 0.01 ）, but the MT rats had less times than MS rats （P 〈 0. 01 ）. The hippocampal GR expression in MS group showed significantly decreased as compared to the control group （ P 〈 0. 05 ）, but no significant difference between MT group and control group. Conclusion Maternal separation could led to impaired behavior development and decreased hippocampal glucocorticoid receptors expression in rats, and exogenous melatonin could have protective effects on behavioral development through upregulating the glucocorticoid receptors expression in hippocampus.