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Introduction: We studied the effects of two types of early life stress (ELS) on the later response to social defeat stress and vulnerability to stress-induced emotional disorders. The structural alterations of the CA3 pyramidal were also evaluated. Methods and Materials: For early handling (EH) or maternal deprivation (MD), newborn rats were isolated from their mothers for 15min/d or 3h/day on postnatal day (PND) 1-21, respectively. Social defeat (SD) stress consisted of physical and sensory confrontation with an aggressive adult male rat on PND 56-59. On PND 61-65, animals from different groups were subjected to open-field test, elevated plus-maze and forced swim test, and then their brains were dissected out and processed for Golgi-cox staining. Results: Social defeat stress in adult rats led to increased anxiety and depressive-like behaviors, as expected. This was accompanied by reductions in dendritic spines and the size of CA3 hippocampal neurons. Early handling ameliorated both behavioral and structural alterations caused by social defeat stress. On the other hand, rats that experienced maternal deprivation (MD-SD) displayed intensified behavioral and structural changes compared to socially defeated rats alone. The MD-SD rats also exhibited significant retraction of apical dendrites and pronounced reduction in dendritic spine density. Conclusion: These findings suggest that different types of ELS can impact the risk for affective disorders in response to social stress in adulthood. The changes in dendritic structure and spine density in CA3 neurons highlight potential mechanisms underlying the effects of early life stress on the behavioral response to stress in adulthood. [ABSTRACT FROM AUTHOR]

Introduction: Stress experienced during critical periods of brain development can induce long-lasting changes in brain structure and function, while environmental enrichment (EE) can counteract such changes. The medial prefrontal cortex (mPFC), is highly vulnerable to stress. In this study, we assessed whether EE could mitigate the structural and behavioral consequences of maternal deprivation (MD) and social defeat (SD) stress in rats. Methods and Materials: Male Wistar rats underwent 3 hours/day of maternal deprivation from postnatal day (PND) 1-21, followed by social defeat stress PND 35-38. PND 23-60, rats were housed in either standard cages (3 to 4 rats) or enriched cages (8 to 12 rats). Behavioral tests were conducted on PND 61 (open field test), PND 62 (elevated plus maze test), and PND 63 (three-chambered social interaction test). On PND 100, rat brains were sectioned and stained using the Golgi-Cox method or cresyl violet. The volume and cellular density of the mPFC as well as the morphology of apical and basal dendrites of its pyramidal neurons were evaluated. Results: Maternal deprivation and social defeat led to shrinkage of the mPFC and decreased cellular density. Additionally, a reduction in the length and number of branches in the apical dendritic trees of mPFC pyramidal neurons was observed, partly mitigated by EE. Stressed rats exhibited reduced locomotor activity in the open field test, increased stretch-attend postures from the closed arms in the elevated plus maze test, and reluctance towards social approach and social novelty in the social interaction test. Stressed rats with EE also demonstrated social avoidance in the social interaction test. Conclusion: EE can partially alleviate the structural consequences of chronic stress during critical periods. However, it does not necessarily mitigate the stress-induced behavioral deficits and might even exacerbate them. [ABSTRACT FROM AUTHOR]