Ward Glenn, Xing Hua Cheng, Carnide Nancy, Slivchak Jane, Wainwright Patricia
Department of Health Studies and Gerontology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
Dev Psychobiol. 2004 Dec;45(4):245-50. doi: 10.1002/dev.20029.
Recent studies have compared artificially reared (AR) rats with dam-reared rats on behavioral outcomes but, despite the fact that they are deprived of their mothers during the stress hyporesponsive period (SHRP), little is known about the effects of AR on the development of the stress response. In this study, the corticosterone (CORT) response to a stressor (saline injection ip) on postnatal Day 12 was assessed in rat pups that had been either dam-reared (DR) or artificially reared since Day 5. In the preceding 24 hr, half the pups in the DR group were maternally deprived (DEP). To control for the food deprivation consequent to maternal deprivation in these groups, half the pups in the AR groups also underwent 24-hr food deprivation (DEP). In the nondeprived condition AR pups did not differ from DR pups on untreated CORT levels or on levels at 1-hr poststress (i.e., all rats demonstrated low levels of CORT characteristic of the SHRP). In contrast, both maternally deprived DR pups and food-deprived AR pups exhibited increased untreated CORT levels as well as a significant increase at 30-min poststress, but CORT elevations were lower in the AR groups than in the DR groups. Thus, long-term maternal deprivation through artificial rearing in rats does not affect the reduced CORT levels and reduced CORT responsiveness associated with the SHRP; however, if animals are food deprived, then all show increased basal CORT levels and a greater CORT response to stress, although this response is lower in AR groups than in DR groups. These results suggest that rat pups artificially reared with adequate nutrition will still exhibit the SHRP.
最近的研究比较了人工饲养（AR）大鼠和由母鼠抚养的大鼠的行为结果，然而，尽管它们在应激低反应期（SHRP）被剥夺了母亲的照顾，但关于人工饲养对应激反应发育的影响却知之甚少。在本研究中，对自出生第5天起就由母鼠抚养（DR）或人工饲养的幼鼠，评估了其在出生后第12天对应激源（腹腔注射生理盐水）的皮质酮（CORT）反应。在前24小时，DR组中有一半的幼鼠被剥夺了母鼠照顾（DEP）。为了控制这些组中因母鼠剥夺导致的食物剥夺，AR组中也有一半的幼鼠经历了24小时的食物剥夺（DEP）。在非剥夺条件下，AR幼鼠与DR幼鼠在未处理的CORT水平或应激后1小时的水平上没有差异（即所有大鼠都表现出SHRP特有的低CORT水平）。相比之下，被剥夺母鼠照顾的DR幼鼠和食物被剥夺的AR幼鼠在未处理的CORT水平以及应激后30分钟时都有显著升高，但AR组的CORT升高幅度低于DR组。因此，通过人工饲养对大鼠进行长期母鼠剥夺不会影响与SHRP相关的CORT水平降低和CORT反应性降低；然而，如果动物被剥夺食物，那么所有动物的基础CORT水平都会升高，并且对压力的CORT反应会更大，尽管AR组的这种反应低于DR组。这些结果表明，营养充足的人工饲养幼鼠仍会表现出SHRP。
