Recent reports have indicated that gut microbiota modulates the responses to stress through the microbiota-gut-brain axis in mice, suggesting a connection between gut microbiota and brain function. We hypothesized that the gut microbiota early in life would have an effect on aggressiveness, and examined how gut microbiota affect aggressive behaviors in mice. BALB/c mice were housed in germ-free (GF) and ex-germ-free (Ex-GF) isolators. An aggression test was performed between castrated and a non-castrated mice at 8 weeks of age; the mice were allowed to confront each other for 10 min in strictly contamination-free environments. To evaluate aggressive behavior related to gut microbiota, we orally administered diluted Ex-GF mouse feces to the offspring of GF mice at 0, 6, and 10 weeks. GF mice showed more aggression than Ex-GF mice. Furthermore, GF mice who were administered feces of the Ex-GF group at 0-week-old were less aggressive than the GF mice. These findings suggested that the gut microbiota in the early stages of development was likely to have an effect on aggressiveness. Maintenance of healthy gut microbiota early in life can affect the mitigation of aggressive behavioral characteristics throughout the lifetime.

最近的报告表明，肠道微生物群通过小鼠的微生物群-肠-脑轴调节对压力的反应，表明肠道微生物群与大脑功能之间存在联系。我们假设生命早期的肠道微生物群会对攻击性产生影响，并研究了肠道微生物群如何影响小鼠的攻击行为。BALB/c 小鼠饲养在无菌 (GF) 和前无菌 (Ex-GF) 隔离器中。在 8 周龄时在阉割和未阉割的小鼠之间进行了攻击性测试；允许小鼠在严格无污染的环境中相互面对 10 分钟。为了评估与肠道微生物群相关的攻击行为，我们在 0、6 和 10 周时向 GF 小鼠的后代口服稀释的 Ex-GF 小鼠粪便。GF 小鼠比 Ex-GF 小鼠表现出更多的攻击性。此外，在 0 周龄时给予 Ex-GF 组粪便的 GF 小鼠的攻击性低于 GF 小鼠。这些发现表明，发育早期的肠道微生物群可能对攻击性产生影响。在生命早期维持健康的肠道微生物群可以影响一生中攻击性行为特征的缓解。