Maternal separation induced resilience to depression and spatial memory deficit despite intensifying hippocampal inflammatory responses to chronic social defeat stress in young adult male rats

Understanding stress-induced transmission of peripherally derived factors into the brain and responses in non-neuronal cells

Stress is a significant cause of mental disorders, for which effective treatments remain limited due to an insufficient understanding of its pathogenic mechanisms. Recent research has increasingly focused on non-neuronal cells to elucidate the molecular mechanisms underlying psychopathology. In this review, we summarize the current knowledge on how non-neuronal cells in the central nervous system, including microglia, astrocytes, and oligodendrocytes, respond to peripherally derived stress-related factors and how these responses contribute to the development of mental disorders. A more comprehensive understanding of stress-induced alterations, with careful consideration of the type and timing of stress exposure, will provide fundamental insights into the pathogenesis of diverse stress-related mental disorders.

One-Week Maternal Separation Caused Sex-Specific Changes in Behavior and Hippocampal Metabolomics of Offspring Rats

To investigate the effects of one-week maternal separation (MS) on anxiety- and depression-like behaviors in adolescent and adulthood as well as adult hippocampal metabolomics simultaneously in offspring female and male rats. In the MS group, newborn SD rats were separated from their mothers for 3 h per day from postnatal days (PND) 2 to 8. The open field test (OFT), elevated plus mazes (EPM), novelty suppressed feeding test (NSFT), and forced swimming test (FST) were conducted during adolescence and adulthood. Serum corticosterone, mRNA expression of hippocampal inflammatory cytokines, and hippocampal untargeted metabolomics of offspring adult rats were examined using an assay kit, qRT-PCR, and UPLC-Q-TOF/MS. Both MS female and male rats showed similar behaviors in OFT, EPM, NSFT, and SPT, except for the latency to feeding during adolescence and the open arm entries during adulthood, showed statistical significance only in MS female rats. Serum corticosterone and hippocampal pro-inflammatory cytokines IFN-γ were significantly elevated in both female and male rats, and IL-1β and TNF-α were significantly increased only in female rats. In hippocampal metabolism, the identification of differential metabolites displayed 53 and 37 in female rats and male rats, respectively (with 35 common metabolites), which were involved in 33 and 30 metabolic pathways with 28 common pathways. One-week MS induced sex-specific anxiety- and depression-like behaviors in female and male offspring rats during adolescence and adulthood, as well as sex-differentiated characteristics in the hippocampus inflammatory cytokines and metabolomics of adult MS rats. From the experimental data, the effects of MS on the female offspring rats were more severe than those of the male offspring rats.

Alterations to the copulatory sequence in young adult male Sprague-Dawley rats administered a ketogenic diet

Ketogenic diets (KDs) have shown therapeutic potential for a range of neuropsychiatric disorders; however, there is insufficient data regarding the behavioral impacts of KDs in healthy populations. Here, we examined the impact of a KD on sexual behavior in young adult male Sprague-Dawley rats maintained on either a KD or standard chow diet (SD). We found that KD males exhibited higher mount rates, higher intromission rates (third and fourth tests only), and lower ejaculation likelihood (second test only) compared to SD males. Consequently, it may be that experience-dependent changes in the processing of sexual stimuli are not occurring as efficiently in KD males, thereby yielding the observed copulatory sequence alterations.

Maternal separation regulates sensitivity of stress-induced depression in mice by affecting hippocampal metabolism

Depression is a serious mental illness. Previous studies found that early life stress (ELS) plays a vital role in the onset and progression of depression. However, relevant studies have not yet been able to explain the specific effects of early stress on stress-induced depression sensitivity and individual behavior during growth. Therefore, we constructed a maternal separation (MS) model and administered chronic social frustration stress at different stages of their growth while conducting metabolomics analysis on the hippocampus of mice. Our results showed that the immobility time of mice in the forced swimming test was significantly reduced at the end of MS. Meanwhile, mice with MS experience significantly decreased total movement distance in the open field test and sucrose preference ratio in the sucrose preference test when subjected to chronic social defeat stress (CSDS) during adolescence. In adulthood, the results were the opposite. In addition, we found that level changes in metabolites such as Beta-alanine, l-aspartic acid, 2-aminoadipic acid, and Glycine are closely related to behavioral changes. These metabolites are mainly enriched in Pantothenate, CoA biosynthesis, and Beta Alanine metabolism pathways. Our experiment revealed that the effects of ELS vary across different age groups. It will increase an individual's sensitivity to depression when facing CSDS in adolescence, but it will reduce their sensitivity to depression when facing CSDS in adulthood. This may be achieved by regulating the hippocampus's Pantothenate and CoA biosynthesis and Beta Alanine metabolism pathways represented by Beta-alanine, l-Aspartic acid, 2-aminoadipic acid, and Glycine metabolites.

Annual Research Review: Early intervention viewed through the lens of developmental neuroscience

The overarching goal of this paper is to examine the efficacy of early intervention when viewed through the lens of developmental neuroscience. We begin by briefly summarizing neural development from conception through the first few postnatal years. We emphasize the role of experience during the postnatal period, and consistent with decades of research on critical periods, we argue that experience can represent both a period of opportunity and a period of vulnerability. Because plasticity is at the heart of early intervention, we next turn our attention to the efficacy of early intervention drawing from two distinct literatures: early intervention services for children growing up in disadvantaged environments, and children at elevated likelihood of developing a neurodevelopmental delay or disorder. In the case of the former, we single out interventions that target caregiving and in the case of the latter, we highlight recent work on autism. A consistent theme throughout our review is a discussion of how early intervention is embedded in the developing brain. We conclude our article by discussing the implications our review has for policy, and we then offer recommendations for future research.

Adolescent nonpharmacological interventions for early-life stress and their mechanisms

Those with a negative experience of psychosocial stress during the early stage of life not only have a high susceptibility of the psychiatric disorder in all phases of their life span, but they also demonstrate more severe symptoms and poorer response to treatment compared to those without a history of early-life stress. The interventions targeted to early-life stress may improve the effectiveness of treating and preventing psychiatric disorders. Brain regions associated with mood and cognition develop rapidly and own heightened plasticity during adolescence. So, manipulating nonpharmacological interventions in fewer side effects and higher acceptance during adolescence, which is a probable window of opportunity, may ameliorate or even reverse the constantly deteriorating impact of early-life stress. The present article reviews animal and people studies about adolescent nonpharmacological interventions for early-life stress. We aim to discuss whether those adolescent nonpharmacological interventions can promote individuals' psychological health who expose to early-life stress.

Investigating the Effects of Maternal Separation on Hypothalamic-Pituitary-Adrenal Axis and Glucose Homeostasis under Chronic Social Defeat Stress in Young Adult Male Rat Offspring

INTRODUCTION

Given the suggested metabolic regulatory effects of stress-responsive genes and based on the impacts of early-life stress on HPA axis development, this study aimed to characterize the maternal separation (MS) impact on the communication between glucose metabolism and HPA axis dysregulations under chronic social defeat stress (CSDS).

METHODS

During the first 2 weeks of life, male Wistar rats were either exposed to MS or left undisturbed with their mothers (Std). Starting on postnatal day 50, the animals of each group were either left undisturbed in the standard group housing (Con) or underwent CSDS for 3 weeks. There were four groups (n = 10/group): Std-Con, MS-Con, Std-CSDS, and MS-CSDS.

RESULTS

Early and/or adult life adversity reduced β-cell number, muscular FK506-binding protein 51 (FKBP51) content, and BMI in adulthood. The reduction of β-cell number and BMI in the MS-CSDS rats were more profound than MS-Con group. CSDS either alone or in combination with MS reduced locomotor activity and increased and decreased corticotropin-releasing factor type 1 receptor (CRFR1) content, respectively, in hypothalamus and pancreas. Although, under CSDS, MS intensified HPA axis overactivity and reduced isolated islets' insulin secretion, it could promote resilience to depression symptoms. No differences were observed in hypothalamic Fkbp5 gene DNA methylation and glucose tolerance among groups.

CONCLUSION

MS exacerbated HPA axis overactivity and the endocrine pancreas dysfunctions under CSDS. The intensified corticosterone secretion and the diminished content of pancreatic CRFR1 protein could be involved in the reduced β-cell number and islets' insulin secretion under CSDS. The decreased muscular FKBP51 content might be a homeostatic response to slow down insulin resistance development under chronic stress.