Spontaneous exploration behavior was examined using the open-field test. As shown in Fig. 1c, the freezing time of the intruder mice increased dramatically at days 1 and 3 after stimulation compared with the control mice (F = 4.46, p < 0.01). At day 7 after stimulation, the freezing time of the intruder mice was shorter than that at day 1 after stimulation (F = 4.46, p < 0.05) but was longer than that of the control mice (F = 4.46, p < 0.05). The freezing time of the intruder mice at day 15 after social stimulation was the same as that of the control mice (F = 4.46, p > 0.05). The above data suggests that aversive information from acute stimulation is maintained at least for 7 days before gradually diminishing. The intruder mice recovered their exploratory behavior at 15 days after social defeat. The time spent on the social interaction zone is shown in Fig. 1b, d. At day 1 and day 3 after social aggression, intruder mice spent less time on the interaction zone compared with the control mice (F = 8.98, p < 0.01). On day 7 after stimulation, intruder mice spent more time on the interaction zone than on days 1 and 3 (F = 8.98, p < 0.05) but still spent less on the interaction zone than control mice (F = 8.98, p < 0.05). On day 15 after stimulation, the intruder mice spent the same time on the interaction zone as control mice (F = 8.98, p > 0.05). These data suggest that information for social defeat stress from acute social aggression is maintained for 7 days before diminishing.Fig. 1Behavioral changes after acute social aggressive stimulation. a Diagram of social aggression and social behavioral test. Social aggression is based on the resident (KM mouse)—intruder (C57B6/L mouse) paradigm. b Representative images of the track during social interaction. c Freezing time in the open field. On days 1 and 3 after stimulation, the freezing time of intruder mice was longer than that of control mice. On day 7 after stimulation, the freezing time of intruder mice was shorter than that at day 1 after stimulation but remained longer than that of control mice, one way ANOVA with Tukey’s test was used, F = 4.46, *p < 0.05, **p < 0.01 compared with control, n = 12. d Time spent in the social interaction zones. On days 1 and 3 after stimulation, intruder mice spent less time in the interaction zone than the control mice. On day 7 after stimulation, intruder mice spent more time in the interaction zone than at days 1 and 3 after stimulation but still spent less time in the interaction zone than control mice, one way ANOVA with Tukey’s test was used, F = 8.98, *p < 0.05, **p < 0.01 compared with control, n = 12