Introduction: According to literature, early stress may lead to a higher susceptibility to the action of various stressors later in life, thus largely contributing to the development of a wide range of affective disorders. Disrupting maternal care is one way to destabilize the environment for pups, which may result in the formation of an altered reaction to acute or moderate stress. Methods: In this study, we analyzed the effects of limited bedding and nesting material (LBN) in PND2-PND9 on baseline gene expression in the hippocampus and frontal cortex of 1-month old rats and the expression of the same genes under conditions of 60-minute restraint. Among the analyzed genes, some were associated with glucocorticoids (Nr3c1 and Nr3c2), others with the activation of the immune system (Nfkbia, Ccl2, Il1b, Il6, Tnfα, Cx3cl1, Cx3cr1, and Ncf1), and yet others with the activation of neuronal networks under stress (Cfos, Ier-2). Gene expression was assessed using real-time PCR (RT-PCR). Results: Exposure to LBN during early postnatal life significantly increased baseline expression of the Fos gene in the amygdala of adolescent rats. LBN exposure more slightly affected the expression of other analyzed genes (Nr3c1, Cx3cl1, Ier2, Ncf1) or evoked alterations of their expression in this group only after exposure to acute restraint stress. The hyperglycemic response to acute restraint was attenuated in LBN-exposed animals, while corticosterone levels were comparable to controls. Among the studied genes, the expression of Nfkbia, Il6, and Tnf was primarily influenced by acute restraint stress, independently of LBN history. The amygdala and ventral hippocampus were the brain regions where the expression of the analyzed genes appeared most sensitive to the experimental manipulations. Conclusion: These data indicate that early-life stress induced by LBN leads to a sustained increase in baseline Fos expression in the amygdala and alters the metabolic response to acute stress in adolescence. The findings further suggest that the amygdala and ventral hippocampus are key regions where the expression of a limited set of stress-related genes is modulated by the interplay of early-life adversity and acute stress. This points to a potential role for amygdalar circuits in the altered stress reactivity observed following adverse early-life conditions.
Deryabina et al. (Fri,) studied this question.