One KM mouse raised alone in a cage for 2 weeks was designated as the resident. The C57BL/6 mice were randomly assigned to a control without the social attack (n = 12) and social defeat with the social attack according to the previous methods . In brief, a C57BL/6 mouse was introduced as the intruder. For 10 min, the C57BL/6 mouse was exposed to the cage with the KM mouse. The aggressive attack was stopped using a perforated plastic barrier, which allows for continued visual, auditory and olfactory contact. After 6 h, the barrier was removed and physical contact was allowed for 10 min. After the second attack, the C57BL/6 mouse was placed back in its home cage. Cumulated frequency of attack is about 40 times per mouse. Mice in social defeat were divided into subgroups on the basis of the designated time at which the animals were sacrificed after social aggression (1, 3, 7, and 15 days; n = 12 per subgroup).