Sexual and social development is affected by a complex interplay between genetic makeup and the early-life rearing environment. While many rodent studies focused primarily on the detrimental... Show moreSexual and social development is affected by a complex interplay between genetic makeup and the early-life rearing environment. While many rodent studies focused primarily on the detrimental effects of early-life stress, human literature suggests that genetic susceptibility may not be restricted to negative environments; it may also enhance the beneficial effects of positive rearing conditions. To examine this interaction in a controlled setting, heterozygous mineralocorticoid receptor knockout (MR+/−) mice and control litter mates were exposed to a limited nesting/bedding (LN, impoverished), standard nesting (SN, control) or communal nesting (CN, enriched) paradigm from postnatal day 2–9 (P2-P9). Offspring was monitored for puberty onset between P24-P36 and, in females, maternal care-giving (i.e. as F1) during adulthood, after which basal corticosterone was measured. Different home-cage environments resulted in profound differences in received maternal care and offspring body weight. In male offspring, LN resulted in delayed puberty onset that was mediated by body weight and unpredictability of maternal care received during early development. In female offspring, rearing condition did not significantly alter sexual maturation and had little effect on their own maternal care-giving behavior. Genotype did affect maternal care: female MR+/− offspring exhibited a less active nursing style and upregulated fragmentation during adulthood, irrespective of early life conditions. Basal corticosterone levels were highest in MR+/− mice with a background of LN. Overall, we found a gene-by-environment interaction with respect to basal corticosterone levels, but not for sexual maturation or maternal behavior. Show less
Kentrop, J.; Smid, C.R.; Achterberg, E.J.M.; IJzendoorn, M.H. van; Bakermans-Kranenburg, M.J.; Joëls, M.; Veen, R. van der 2018
Early life context and stressful experiences are known to increase the risk of developing psychiatric disorders later in life, including disorders with deficits in the social domain. Our study... Show moreEarly life context and stressful experiences are known to increase the risk of developing psychiatric disorders later in life, including disorders with deficits in the social domain. Our study aimed to investigate the influence of early life environment on social behavior in a well-controlled animal model. To this end we tested the effects of maternal deprivation (MD) on rat social play behavior in adolescence and social interaction in adulthood. Additionally, we provided a stimulating environment during adolescence (complex housing) as a potential intervention to diminish the effects of early life stress. Male and female Wistar rats were deprived from their mother for 24 h on postnatal day 3 (PND 3) or were left undisturbed. Complex housing started 5 days after weaning and consisted of housing 10 same-sex conspecifics in large, two-floor MarlauTM cages until the end of the study. Social play behavior in adolescence was tested under different conditions (3 h vs. 24 h social isolation prior to testing). Maternally deprived males – but not females – showed a longer latency to play and a decreased total amount of social play behavior, after a 24 h isolation period. In adulthood, social discrimination was impaired in deprived male and female rats in the three-chamber social approach task. Complex housing did not moderate the effects of MD, but in itself induced a strong behavioral phenotype. Both complex housed males and females hardly displayed any play behavior after a 3 h isolation period. However, after 24 h of isolation, these animals showed shorter latencies to engage in social play behavior. Only complex housed males truly showed more social play behavior here, while showing less social interest in adulthood. We conclude that MD has mild negative effects on social behavior in adolescence and adulthood, which are not counteracted by complex housing. Complex housing induces a specific phenotype associated with rapid habituation; a lack of social play after short isolation periods, while increasing play behavior after a prolonged period of isolation in adolescence, and less social interest, paired with intact social discrimination in adulthood. In both early life settings, males seem to be more influenced by the early life environment compared to females. Show less
Kentrop, J.; Van der Tas, L.; Loi, M.; IJzendoorn, M.H. van; Bakermans, M.J.; Joels, M.; Veen, R. van der 2016
