Rosenthal M J, Varela M, Garcia A, Britton D R
Geriatric Research, Education and Clinical Center, Veterans Administration Medical Center, Sepulveda, California 91343.
Exp Gerontol. 1989;24(2):149-57. doi: 10.1016/0531-5565(89)90025-9.
To examine age-related changes in responsiveness to environmental novelty, 3-, 12-, and 24-month-old male Fischer 344 rats were maintained on a restricted diet and exposed to a modified open field for 10 min on each of 10 consecutive days. On the first day of testing, animals of all groups showed equal amounts of rearing. While the 3-month animals continued to show approximately the same levels of rearing until the 8th day, by day 5, the older groups (12- and 24-month) had significantly reduced their rearing. Conversely, grooming was initially highest among the 24-month-old animals. While 3- and 12-month rats showed habituation of grooming, the oldest animals failed to habituate their grooming response by day 5. By day 10, there were no significant differences among the groups in either rearing or grooming. Although food was available in the center of the modified open field, there was little eating and there were no differences among groups. However, all animals did eat quickly when food was made available in their home cages. Thus, all animals displayed a profile of stress-related responses to open field exposure. Plasma corticosterone levels likewise were elevated in the modified open field. Some, but not all, components of this response profile habituated over the 10 days of exposure. Three-month-old animals responded to the novelty predominantly by rearing and 24-month animals predominantly by grooming. This suggests that with aging, locomotor responses to stress are replaced by a more self-directed form of displacement activity.
为研究对环境新奇性反应的年龄相关变化，将3个月、12个月和24个月大的雄性Fischer 344大鼠维持在限食状态，并在连续10天中的每一天暴露于改良旷场10分钟。在测试的第一天，所有组的动物表现出相同程度的竖毛行为。虽然3个月大的动物在第8天之前继续表现出大致相同水平的竖毛行为，但到第5天，年龄较大的组（12个月和24个月）竖毛行为显著减少。相反，理毛行为最初在24个月大的动物中最为频繁。虽然3个月和12个月大的大鼠理毛行为出现习惯化，但最年长的动物到第5天仍未使其理毛反应习惯化。到第10天，各组在竖毛或理毛行为上均无显著差异。尽管在改良旷场中央提供了食物，但进食很少，且各组之间没有差异。然而，当在其笼舍中提供食物时，所有动物都进食很快。因此，所有动物对旷场暴露均表现出与应激相关的反应模式。在改良旷场中，血浆皮质酮水平同样升高。在10天的暴露过程中，这种反应模式的一些但并非全部成分出现了习惯化。3个月大的动物对新奇性主要通过竖毛做出反应，而24个月大的动物主要通过理毛做出反应。这表明随着年龄增长，对应激的运动反应被一种更自我导向的替代活动形式所取代。
