Behavioral phenotype of C57Bl/6 mice that endured bullying during infant age period

Abstract

BACKGROUND: According to UNESCO data for 2018, every third student is involved in bullying. To study the impact of social conflicts on the state of the nervous system the K. Michek model of chronic social stress was used, but the study of the effects of chronic social stress on prepubertal animals has not been conducted. AIM: To analyze the effect of chronic stress in infant age period to the behavioral phenotype of C57Bl/6 mice in early and long-term periods. MATERIALS AND METHODS: The objects of the study were male C57Bl/6 mice (n=48). For bullying modeling we chose chronic social stress in infant age period from 20 to 29 postnatal day (P20–P29) according to the “resident–intruder” scheme. Mice were divided into two subgroups to study the early (P31–P35, infant age period) and long-term (P57–P74, adulthood) consequences of chronic social stress. For the behavioral phenotyping we used the following tests: “open field” test, three-chamber social test, object recognition test, passive avoidance task and Barnes maze. RESULTS: Bullying modeling led to the changes in the behavioral phenotype both in infant age and in adulthood. The behavioral phenotype in infant age period was characterized by increased social activity and recognition, high anxiety, decreased locomotor and exploratory activity, impaired recognition of inanimate objects, but good characteristics of learning, working and long-term memory. In adulthood, the behavioral phenotype of mice retained high anxiety, low level of exploratory activity, good learning and memory characteristics, decline in social recognition in three-chamber test, while the recognition of inanimate objects was preserved at the same level. CONCLUSION: Chronic social stress in infant age in a mouse model of bullying causes disruption of the behavioral phenotype in infant and adult age. Features of the behavioral phenotype of mice after bullying were an increase in anxiety and social isolation against the background of the ability to learn and good memory.