Social isolation (SI) is a major health risk in older people leading to cognitive decline. This study examined how SI and age influence performance in the novel object recognition (NOR) and elevated plus maze (EPM) tasks in C57BL/6 mice aged 3 or 24 months. Mice were group-housed (groups of 2–3) or isolated for 2 weeks prior to experimentation. Following NOR and EPM testing hippocampal norepinephrine (NE), 5, hydroxytryptamine (5-HT), 5, hydroxyindole acetic acid (5-HIAA), corticosterone (CORT) and interleukin-6 (IL-6) were determined and serum collected for basal CORT analysis. A separate set of mice were exposed to the forced swim test (FST), sacrificed immediately and serum CORT determined. SI impaired performance in the NOR and the FST, reduced hippocampal 5-HT, increased hippocampal IL-6 and increased serum CORT post-FST in young mice. Aged mice either failed to respond significantly to SI (NOR, FST, hippocampal 5-HT, serum CORT post FST) or SI had synergistic effects with age (hippocampal NE, 5-HIAA:5-HT). In conclusion, the lack of response to SI in the aged mice may affect health by preventing them adapting to new stressors, while the synergistic effects of SI with age would increase allostatic load and enhance the deleterious effects of the ageing process.

社会孤立 (SI) 是老年人的主要健康风险，导致认知能力下降。本研究检查了 SI 和年龄如何影响 3 个月或 24 个月大的 C57BL/6 小鼠在新物体识别 (NOR) 和高架十字迷宫 (EPM) 任务中的表现。实验前将小鼠群养（每组 2-3 只）或隔离 2 周。NOR 和 EPM 检测海马去甲肾上腺素 (NE)、5、羟色胺 (5-HT)、5、羟吲哚乙酸 (5-HIAA)、皮质酮 (CORT) 和白细胞介素-6 (IL-6) 后，测定并收集血清用于基础 CORT 分析。一组单独的小鼠接受强迫游泳试验 (FST)，立即处死并测定血清 CORT。SI 损害了 NOR 和 FST 的表现，减少了海马 5-HT，增加了海马 IL-6，并增加了年轻小鼠 FST 后血清 CORT。老年小鼠对 SI 没有显着反应（NOR、FST、海马 5-HT、FST 后血清 CORT）或 SI 与年龄（海马 NE、5-HIAA：5-HT）具有协同效应。总之，老年小鼠对 SI 缺乏反应可能会通过阻止它们适应新的压力源来影响健康，而 SI 与年龄的协同作用会增加稳态负荷并增强衰老过程的有害影响。