Leuner Benedetta, Shors Tracey J
Department of Psychology and Center for Collaborative Neuroscience, Rutgers University, 152 Frelinghuysen Road, Piscataway, NJ 08854, USA.
Horm Behav. 2006 Jun;50(1):38-51. doi: 10.1016/j.yhbeh.2006.01.002. Epub 2006 Feb 20.
Hormonal and emotional responses to stress are diminished during pregnancy and the postpartum period. However, the effects of stress on learning during these stages of the female life span have not been examined. In previous studies, we have reported that exposure to an acute stressful event reduces classical eyeblink conditioning 24 h later in adult virgin female rats that are experiencing an ovarian cycle. Here we show that conditioning during late pregnancy was similarly reduced by stressful experience. However, conditioning in postpartum females was unaffected by stressor exposure. The resistance to stress during the postpartum period was evident as early as 2 days after parturition and persisted until the late postpartum period, just prior to weaning. Postpartum conditioning was unresponsive to numerous types of stressors, including brief inescapable tailshocks, swim stress, and exposure to a male intruder. The resistance to stress appears to be dependent on the presence of the offspring, because the impairment in conditioning returned when postpartum females were separated from their pups. Moreover, the resistance to stress occurred in virgin females that behaved maternally after being exposed to young pups for several days. Together, these data suggest that the presence of offspring and the nurturing and care-giving activities that they elicit protect females from the adverse effect of stress on processes involved in learning and memory.
在孕期和产后阶段，机体对压力的激素和情绪反应会减弱。然而，压力对女性生命周期这些阶段学习能力的影响尚未得到研究。在之前的研究中，我们报告称，成年未孕雌性大鼠在经历卵巢周期时，暴露于急性应激事件会在24小时后降低经典眨眼条件反射。在此我们表明，孕期后期的条件反射同样会因应激经历而降低。然而，产后雌性大鼠的条件反射不受应激源暴露的影响。产后对应激的抵抗力早在分娩后2天就很明显，并一直持续到产后晚期，即断奶前。产后条件反射对多种类型的应激源无反应，包括短暂的不可逃避的尾部电击、游泳应激以及暴露于雄性入侵者。对应激的抵抗力似乎取决于后代的存在，因为当产后雌性大鼠与幼崽分离时，条件反射的损伤又会出现。此外，在接触幼崽数天后表现出母性行为的未孕雌性大鼠中也出现了对应激的抵抗力。总之，这些数据表明，后代的存在以及它们引发的养育和照料活动可保护雌性免受压力对学习和记忆相关过程的不利影响。
