Early life experience is closely related to depression caused by stress in adulthood. Early life experience, including maternal separation (MS), has been shown to evoke stress sensitivity to depression upon re-exposure to stress in adults. However, MS has also been shown to lead to resilience to stress-induced depression, which is contradictory and rarely studied. To investigate the effects of MS on depression in adults and the related mechanism, male C57/BL6J mouse pups were exposed to different MS procedures from postnatal day (PD)1 to PD21. Body weight (BW) measurements and behavioural tests (the forced swimming test (FST) and open field test (OFT)) were performed on PD41 to explore depressive and anxiety-like behaviours. Then, as adults, the mice were exposed to chronic unpredictable mild stress (CUMS) for 28 days, and then behavioural tasks were recorded. After CUMS exposure, the mice in the MS180 group (which were separated from their mothers for 3 h on PD1-PD21) showed significantly decreased time spent in the centre of the open field and reduced velocity in the OFT, a reduced latency to immobility in the FST, and decreased BW. However, the mice in the MS15 group (which were separated from their mothers for 15 min on PD1-PD21) performed similarly to NSNC mice (which were not separated from their mothers) in the behavioural tests. We further found that the expression of Iba1, a marker of neuroinflammation, was increased in the MS180 group but not in the MS15 group. In addition, our study showed decreased mRNA and protein expression of CRMP2, an important neuroprotective factor, in the MS180 group, but CRMP2 expression was unchanged in the MS15 group. This study confirmed the generation of different behavioural responses to stress exposure in adulthood due to different degrees of MS. Neuroinflammation and neuroprotection are involved, which requires further research.

早期生活经历与成年后的压力导致的抑郁症密切相关。早期的生活经验，包括母体分离（MS），已证明在成年人再次暴露于压力时会引起对抑郁的压力敏感性。但是，MS也被证明可以抵抗压力引起的抑郁，这是自相矛盾的，很少进行研究。为了研究MS对成人抑郁症的影响及其相关机制，从出生后第一天（PD）1到PD21，将雄性C57 / BL6J幼鼠暴露于不同的MS程序。对PD41进行了体重（BW）测量和行为测试（强迫游泳测试（FST）和野外测试（OFT）），以探索抑郁和焦虑症行为。然后，成年后，小鼠暴露于慢性不可预测的轻度应激（CUMS）28天，然后记录行为任务。在CUMS暴露后，MS180组的小鼠（在PD1-PD21上与其母体分开3小时）显示出在旷野中心花费的时间显着减少，在OFT中的速度降低了，从而降低了小鼠静止的潜伏期。 FST，并降低了体重。但是，在行为测试中，MS15组的小鼠（在PD1-PD21上与母亲分离15分钟）的行为与NSNC小鼠（与母亲没有分离）相似。我们进一步发现，神经炎性标志物Iba1的表达在MS180组中增加，但在MS15组中没有增加。此外，我们的研究显示，MS180组中重要的神经保护因子CRMP2的mRNA和蛋白表达降低，而MS15组中CRMP2的表达保持不变。这项研究证实，由于不同程度的MS，对成年后的压力暴露会产生不同的行为反应。涉及神经炎症和神经保护，这需要进一步研究。