Extended Effect of Chronic Social Defeat Stress in Childhood on Behaviors in Adulthood

Abstract

Individuals exposed to social stress in childhood are more predisposed to developing psychoemotional disorders in adulthood. Here we use an animal model to determine the influence of hostile social environment in adolescence on behavior during adult life. One-month-old adolescent male mice were placed for 2 weeks in a common cage with an adult aggressive male. Animals were separated by a transparent perforated partition, but the adolescent male was exposed daily to short attacks from the adult male. After exposure to social stress, some of the adolescent mice were placed for 3 weeks in comfortable conditions. Following this rest period, stressed young males and adult males were studied in a range of behavioral tests to evaluate the levels of anxiety, depressiveness, and communicativeness with an unfamiliar partner. In addition, adult mice exposed to social stress in adolescence were engaged in agonistic interactions. We found that 2 weeks of social stress result in a decrease of communicativeness in the home cage and diminished social interactions on the novel territory. Stressed adolescents demonstrated a high level of anxiety in the elevated plus-maze test and helplessness in the Porsolt test. Furthermore, the number of dividing (BrdU-positive) cells in the subgranular zone of the dentate gyrus was significantly lower in stressed adolescents. After 3 weeks of rest, most behavioral characteristics in different tests, as well as the number of BrdU-positive cells in the hippocampus, did not differ from those of the respective control mice. However, the level of anxiety remained high in adult males exposed to chronic social stress in childhood. Furthermore, these males were more aggressive in the agonistic interactions. Thus, hostile social environment in adolescence disturbs psychoemotional state and social behaviors of animals in adult life.

Exposure to social defeat stress in adolescence improves the working memory and anxiety-like behavior of adult female rats with intrauterine growth restriction, independently of hippocampal neurogenesis

“…Other studies report that after SDS, depressionlike behavior is significantly augmented in both male and female rats (Bourke and Neigh, 2011), and that working memory is significantly reduced in male rats (Novick et al, 2013). Concerning neurogenesis in male rats exposed to SDS in adolescence, hippocampal cellular proliferation has been reported by two groups to be unchanged (Buwalda et al, 2013;Kovalenko et al, 2014), while another group reports it to be significantly reduced (Van Bokhoven et al, 2011). Considering these reports in male rats in the context of the notion of stress-induced reduction in neuronal plasticity (Gould and Tanapat, 1999), our finding of increased neural differentiation in female rats in the present study may seem surprising.…”

“…The long-term effects of adolescent SDS on behavioral, neurogenic, and endocrine responses in non-IUGR adults remain controversial. One study found that anxiety-like behavior remained unchanged in male and female rats (Bourke and Neigh, 2011), while others found it to be significantly reduced (Watt et al, 2009) or increased (Kovalenko et al, 2014) in male rats exposed to SDS in adolescence. Other studies report that after SDS, depressionlike behavior is significantly augmented in both male and female rats (Bourke and Neigh, 2011), and that working memory is significantly reduced in male rats (Novick et al, 2013).…”

“…Notably, despite significant behavioral changes, there were no alterations in hippocampal neurogenesis in IUGR female rats as a consequence of exposure to SDS in this study. In non-IUGR mammals, some studies have documented correlations between hippocampal neurogenesis and a variety of behavioral responses (McCormick et al, 2010;Ming and Song, 2011;Samuels and Hen, 2011), while others report a dissociation between neurogenesis and behavioral changes (Henn and Vollmayr, 2004;Kovalenko et al, 2014). Taken together, the data seem to suggest that neurogenesis-independent mechanisms (David et al, 2009) are likely to be involved in the rescue of cognitive impairment and anxiogenic responses in IUGR female rats that are due to adolescent exposure to SDS.…”

“…The social impact of IUGRrelated learning and emotional difficulties manifests at school age or in adolescence (Alati et al, 2009;Geva et al, 2006a,b;Leitner et al, 2007;O'Keeffe et al, 2003;Scherjon et al, 2000;Vasiliadis et al, 2010), and these difficulties are undoubtedly precursors of adult psychopathology. In normal rats, the adolescent period in particular is considered to be one that is sensitive to stressors (Bingham et al, 2011), and stressors are generally thought to increase the risk of developing behavioral disorders in adulthood (Kovalenko et al, 2014). This is because of the relatively late maturation of brain areas that are targeted by stress, such as the prefrontal cortex and the hippocampus.…”

Potential of Environmental Enrichment to Prevent Transgenerational Effects of Paternal Trauma

“…Resilience is a form of adaptive response manifested by active or passive coping in adverse conditions (Franklin et al, 2012) that can follow previous trauma exposure. For instance, social avoidance is viewed as an active coping behavior that can be manifested by an adult individual after being exposed to traumatic stress in early postnatal life (Franklin et al, 2011) or chronic social defeat in adulthood (Kovalenko et al, 2014). In the case of early traumatic stress, social avoidance has been shown to be accompanied by altered behavioral flexibility, and both are transmitted to the progeny (Franklin et al, 2011;Gapp et al, 2014b).…”