青少期社会隔离和不确定性应激对大鼠成年后情绪行为的影响

Adolescent social isolation and unpredictable stress have different effects on emotional behaviors in adult rats

目的分别观察青少期社会隔离和不确定性应激对大鼠成年后情绪行为的影响。方法在青少期(出生后28 d^41 d)分别给予研究组大鼠2周社会隔离应激或不确定性复合应激,应激后经3周恢复至所有大鼠进入成年期后检测其情绪行为改变。采用糖水偏好测试和强迫游泳检测大鼠的抑郁样行为,采用旷场试验和高架十字迷宫试验检测焦虑样行为。结果与群养组相比,青少期社会隔离组大鼠成年后的所检测的各项情绪行为均无明显差异(P>0.05)。经历青少期不确定性应激的成年大鼠与其对照组相比糖水偏好指数没有明显改变[(0.86±0.19)vs(0.86±0.03),P>0.05],但在强迫游泳测试中表现出更多的绝望行为(强迫游泳不动行为增加)[(29.88±3.37)vs(19.90±3.19),P<0.05]、更少的主动行为(挣扎行为减少)[(24.00±1.67)vs(32.90±3.09),P<0.05],提示该应激并不影响大鼠成年后偏好糖水的本能行为,但导致其急性应激应对能力受损,对成年应激事件更容易发展出次级的应对无能或绝望的抑郁样行为。不确定性应激研究组的大鼠成年后在高架十字迷宫测试中较其对照组闭合臂停留时间明显增加[(176.90±17.01)vs(136.48±9.47),P<0.05]以及开放臂进入次数明显减少[(3.00±0.93)vs(5.90±1.08),P<0.05],提示该应激增加了大鼠成年后的焦虑样行为水平。结论青少期社会隔离应激和不确定性应激对大鼠成年后情绪行为的影响存在差异,青少期不确定性应激能够有效诱导大鼠多项情绪行为显著和持续的改变,提供了一种青少期应激增加成年大鼠应激性抑郁易感性的动物模型。

Objective To investigate the effects of social isolation and unpredictable stress during adolescence on adult emotional behaviors in rats. Methods Male SD rats were given 2-week social isolation or unpredictable stress during adolescence （ postnatal day 28 - 41, PND28 - 41 ）. After a 3-week recovery, a variety of emotional behaviors were tested in rats during adulthood. Sucrose preference test and forced swim test （FST） were used to evaluate depression-like behaviors, while open field and elevated plus-maze （EPM） were used to evaluate anxiety-like behaviors. Results Adolescent social isolation had no effects on all tested emotional behaviors of adult rats （ P 〉 0. 05）. Unpredictable stress during adolescence had no effect on sucrose preference of adult rats [ （0. 86 ±0. 19） vs （0. 86±0. 03）, P 〉0. 05] , while increased immobility behavior [ （29. 88 ±3.37 ） vs （ 19. 90 ±3.19）, P 〈 0. 05 ] and decreased climbing behavior [ （24. 00± 1.67 ） vs （32. 90 ± 3.09） ,P 〈 0.05] in FST, which suggested that adolescent unpredictable stress did not affect intrinsic preference for sucrose of adult rats, but impaired behaviors implicated in motivation and stress coping. Rats exposed to adolescent un- predictable stress developed highly significant despair behaviors after acute severe stress in adulthood. In addition, adult rats exposed to unpredictable stress during adolescence showed more closed arm entries [ （ 176. 90± 17.01 ） vs （ 136.48 ±9. 47）, P 〈 0. 05 ] and less open arm entries [ （ 3.00± 0. 93 ） vs （ 5. 90 ±1.08）, P 〈 0. 05 ], demonstrating an increased levels of anxious behaviors. Conclusions Social isolation and unpredictable stress during adolescence have different effects on adult emotional behaviors in rats. Unpredictable stress can effectively induce profound and long-lasting changes of emo- tional behaviors. The present study suggests that ＂adolescent unpredictable stress＂ model may serve as an adolescent stress- induced animal model of depression.