Early Maternal Separation Research Articles

Late maternal separation provides resilience to chronic variable stress-induced anxiety- and depressive-like behaviours in male but not female mice

Maternal separation can have long-lasting effects on an individual’s susceptibility to stress later in life. Maternal separation during the postnatal period is a commonly used paradigm in rodents to investigate the effects of early life stress on neurobehavioural changes and stress responsiveness. However, maternal separation during stress hyporesponsive and responsive periods of postnatal development may differ in its effects on stress resilience. Therefore, we hypothesised that late maternal separation (LMS) from postnatal day 10 to 21 in mice may have different effect on resilience than early maternal separation during the first week of postnatal life. Our results suggested that male LMS mice are more resilient to chronic variable stress (CVS)-induced anxiety and depressive-like behaviour as confirmed by the open field, light-dark field, elevated plus maze, sucrose preference and tail suspension tests. In contrast, female LMS mice were equally resilient as non-LMS female mice. We found increased expression of NPY, NPY1R, NPY2R, NPFFR1, and NPFFR2 in the hypothalamus of male LMS mice whereas the opposite effect was observed in the hippocampus. LMS in male and female mice did not affect circulating corticosterone levels in response to psychological or physiological stressors. Thus, LMS renders male mice resilient to CVS-induced neurobehavioural disorders in adulthood.

Network pharmacology- and molecular docking-based investigation on the mechanism of action of Si-ni San in the treatment of depression combined with anxiety and experimental verification in adolescent rats.

The incidence rate of adolescent depression and anxiety has been increasing since the outbreak of COVID-19, which there are no effective therapeutic drugs available. Si-ni San is commonly used in traditional Chinese medicine for the treatment of depression-like as well as anxiety-like behavior, but its mechanism for treating depression combined with anxiety during adolescence is not yet clear. Network pharmacology was used to explore potential drug molecules and related targets, molecular docking and molecular dynamics (MD) simulation were used to evaluate the interaction between the potential drug molecules and related targets, and a model of anxiety combined with depression in adolescent rats as well as the following behavioral tests and molecular biology tests were used to verify the results from network pharmacology and molecular docking. As a result, 256 active ingredients of Si-ni San and 1128 potential targets were screened out. Among them, quercetin, Luteolin, kaempferol, 7-Methoxy-2-methyl isoflavone, formononetin showed to be the most potential ingredients; while STAT3, IL6, TNF, AKT1, AKT1, TP53, IL1B, MAPK3, VEGFA, CASP3, MMP9 showed to be the most potential targets. AGE-RAGE signaling pathway in diabetic complications, IL-17 signaling pathway, HIF-1 signaling pathway, PI3K-Akt signaling pathway and TNF signaling pathway, which are involved in anti-inflammation processes, showed to be the most probable pathways regulated by Si-ni San. Molecular docking and MD simulation between the compounds to inflammation-associated targets revealed good binding abilities of quercetin, Luteolin, kaempferol, nobiletin and formononetin to PTGS2 and PPARγ. In the experiment with adolescent rats, Si-ni San markedly suppressed early maternal separation (MS) combined with adolescent chronic unpredictable mild stress (CUMS)-induced depression combined with anxiety. The qPCR results further indicated that Si-ni San regulated the oxidative stress and inflammatory response. This study demonstrates that adolescent anxiety- and depression-like behavior induced by MS combined CUMS can be ameliorated by Si-ni San by improved inflammation in hippocampus via targeting TNF pathway and Nrf2 pathway, helping to reveal the mechanism of Si-ni San in treating adolescent depression combined with anxiety.

Enhanced harm detection following maternal separation: Transgenerational transmission and reversibility by inhaled amiloride.

Early-life adversities are associated with altered defensive responses. Here, we demonstrate that the repeated cross-fostering (RCF) paradigm of early maternal separation is associated with enhancements of distinct homeostatic reactions: hyperventilation in response to hypercapnia and nociceptive sensitivity, among the first generation of RCF-exposed animals, as well as among two successive generations of their normally reared offspring, through matrilineal transmission. Parallel enhancements of acid-sensing ion channel 1 (ASIC1), ASIC2, and ASIC3 messenger RNA transcripts were detected transgenerationally in central neurons, in the medulla oblongata, and in periaqueductal gray matter of RCF-lineage animals. A single, nebulized dose of the ASIC-antagonist amiloride renormalized respiratory and nociceptive responsiveness across the entire RCF lineage. These findings reveal how, following an early-life adversity, a biological memory reducible to a molecular sensor unfolds, shaping adaptation mechanisms over three generations. Our findings are entwined with multiple correlates of human anxiety and pain conditions and suggest nebulized amiloride as a therapeutic avenue.

Effects of early maternal separation on the expression levels of hippocampal and prefrontal cortex genes and pathways in lactating piglets.

In actual production, due to increased litter size when raising pigs, the management of piglets by split-suckling leads to intermittent neonatal maternal separation (MS). Early lactation is a critical period for the cognitive development of the brain of newborn piglets, and we hypothesized that intermittent MS may affect piglets' neurodevelopment and cognitive ability. To determine the effects of the MS, we selected hippocampal and prefrontal cortex (PFC) tissues from piglets for the detection of neurodevelopmental or cognitive related indicators, the control group (Con group, n = 6) was established with no MS and an experimental group (MS group, n = 6) was established with MS for 6 h/day. Piglets in the MS group were milk-supplemented during the separation period and all piglets in both treatment groups were weaned at postnatal day (PND) 35. On PND 35, three male piglets from each group were sacrificed for hippocampus and PFC samples used for reference transcriptome sequencing. Following bioinformatics analysis, Gene ontology (GO) enrichment, Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, and candidate gene screening and pathway were performed for differentially expressed genes. The results showed that a total of 1,632 differential genes were identified in the hippocampus of the MS group, including 1,077 up-regulated differential genes, 555 down-regulated differential genes, and 655 significant GO entries. Analysis of the PFC of the MS group revealed 349 up-regulated genes, 151 down-regulated differential genes, and 584 significant GO entries. Genes associated with neurodevelopment were screened for large fold differences in the hippocampus, and genes associated with cognition were screened for large fold differences in the PFC. Quantitative real-time PCR (qRT-PCR) was used to verify the sequencing data. Western blot (WB) experiments revealed that MS inhibited the neurodevelopment-related WNT signaling pathway in the hippocampus and the cognitive-related PI3K-AKT signaling pathway in the PFC. Taken together, these findings suggest that intermittent MS may affect some cognitive functions in piglets by damaging hippocampal and PFC genes or pathways.

Risky decision-taking task: A novel paradigm to assess the risk-taking behaviour in rats predisposed to early-life stress

One of the characteristic features of adolescence is risk-taking behavioural traits. Uncontrolled risk-taking without proper assessment may have harmful impact on mental health later in life. Therefore, it is essential to identify it early for the preventable health problems. In the present study, we have designed a novel paradigm, viz. Risky Decision-taking Task (RDTT), to evaluate the spontaneous risk-taking behavioural repertoire in adolescent rodents. The task was designed based on both risk and cognitive factors. To validate and compare the risk-taking tendency, we have used early maternal separation and isolation (MS) stress model, as it is known to increase anxiety and curiosity-like behaviour at adolescence. We have used Sprague-Dawley rats of both sexes. Rats were exposed to MS stress for 10 days daily for six hours during stress hyporesponsive period (SHRP) from postnatal day 4–13. These rats were subjected to RDTT during adolescence. This task is a reward-based task where the latency to collect reward in the presence or absence of a risk factor is assessed. It consists of habituation, training to find the location of small and large rewards, reward preference for small and large reward and testing period under risky situation. Rats were trained individually to retrieve the valuation-based rewards under the risky, but innate aversive environments. The results from RDTT showed that as compared to controls, MS rats from both sexes showed reduced latency to collect large reward in the presence of a risk element and a reduced risk-index which is indicative of a higher risk-taking tendency in these rats. In addition, MS rats showed a trend towards anxiety-like behaviour as compared to controls in the Light-Dark Test. These results together show decreased risk latency for the large reward and reduced risk assessment in MS rats which is suggestive of more risk-taking tendency in these rats. Thus, we propose that RDTT paradigm can be used to evaluate the spontaneous risk-taking behavioural repertoire based on innate, spontaneous aversion and cognitive factors in rats.

Effects of early intermittent maternal separation on behavior, physiological, and growth performance in piglets.

In pig production, the management of piglets by batch lactation due to the increase in litter sizes of sows may result in intermittent early neonatal maternal separation (NMS). We speculated that NMS may affect the piglets cognitive growth performance and health. To determine the extent of the effect, 12 litters of crossbred piglets (Large White × Duroc × Min-pig) were used in this trial. Piglets in the control (Con) group (n = 6) were given a standard feeding method during lactation. Piglets in the experimental group (n = 6) were subjected to the NMS model, in which sows were led out of the enclosure with food every day (8:00-11:00 and 13:00-16:00) starting from postnatal day (PND) 7. During the separation, the piglets were supplemented with milk. All experimental piglets were weaned on PND 35. The piglets were observed for aggression, play, mutual sniffing, and exploratory behavior on PNDs 7, 8, 21, 22, 34, 35, 38, 39, 51, 52, 64, and 65. Physiological indicators, namely serum adrenaline, cortisol, interleukin (IL)-1β, IL-4, IL-6, and tumor necrosis factor (TNF)-α were measured on PNDs 35, 38, and 65, while piglet growth performance was evaluated during suckling and 1 month after weaning. The results showed that aggressive behavior in the MS group was significantly higher than that in the Con group (P < 0.05). Playful and mutual sniffing behaviors in the MS group were significantly lower than those in the Con group except for PNDs 38 and 39 (P < 0.05). Active exploratory behavior in the MS group was significantly higher than that in the Con group on PNDs 7 and 8, and PNDs 21 and 22 (P < 0.05). The frequency of belly-nosing behavior was significantly higher in the MS group than that in the Con group except for PNDs 64 and 65 (P < 0.05). Compared with the Con group, epinephrine, IL-1β, IL-6, and TNF-α concentrations on PNDs 35, 38, and 65 were significantly increased in the MS group (P < 0.01), while IL-4 concentration was significantly decreased (PND 35: P < 0.05; PNDs 38 and 65: P < 0.01). Compared with the Con group, the piglet diarrhea rate in the MS group during suckling was significantly increased (P < 0.01), the weaning weight was significantly decreased (P < 0.05), and it had no significant effect on the body weight at the end of the trial (P > 0.05). In conclusion, the early intermittent NMS created stress and affected the growth performance of piglets during suckling. However, the growth rate was improved by compensatory measures during late weaning.

Sex-dependent effects of early life stress on reinforcement learning and limbic cortico-striatal functional connectivity

Major depressive disorder (MDD) is a stress-related condition hypothesized to involve aberrant reinforcement learning (RL) with positive and negative stimuli. The present study investigated whether repeated early maternal separation (REMS) stress, a procedure widely recognized to cause depression-like behaviour, affects how subjects learn from positive and negative feedback. The REMS procedure was implemented by separating male and female rats from their dam for 6 h each day from post-natal day 5–19. Control rat offspring were left undisturbed during this period. Rats were tested as adults for behavioral flexibility and feedback sensitivity on a probabilistic reversal learning task. A computational approach based on RL theory was used to derive latent behavioral variables related to reward learning and flexibility. To assess underlying brain substrates, a seed-based functional MRI connectivity analysis was applied both before and after an additional adulthood stressor in control and REMS rats. Female but not male rats exposed to REMS stress showed increased response ‘stickiness’ (repeated responses regardless of reward outcome). Following repeated adulthood stress, reduced functional connectivity from the basolateral amygdala (BLA) to the dorsolateral striatum (DLS), cingulate cortex (Cg), and anterior insula (AI) cortex was observed in females. By contrast, control male rats exposed to the second stressor showed impaired learning from negative feedback (i.e., non-reward) and reduced functional connectivity from the BLA to the DLS and AI compared to maternally separated males. RL in male rats exposed to REMS was unaffected. The fMRI data further revealed that connectivity between the mOFC and other prefrontal cortical and subcortical structures was positively correlated with response ‘stickiness’. These findings reveal differences in how females and males respond to early life adversity and subsequent stress. These effects may be mediated by functional divergence in resting-state connectivity between the basolateral amygdala and fronto-striatal brain regions.

Effects of iron deficiency and iron supplementation at the host-microbiota interface: Could a piglet model unravel complexities of the underlying mechanisms?

Iron deficiency is the most prevalent human micronutrient deficiency, disrupting the physiological development of millions of infants and children. Oral iron supplementation is used to address iron-deficiency anemia and reduce associated stunting but can promote infection risk since restriction of iron availability serves as an innate immune mechanism against invading pathogens. Raised iron availability is associated with an increase in enteric pathogens, especially Enterobacteriaceae species, accompanied by reductions in beneficial bacteria such as Bifidobacteria and lactobacilli and may skew the pattern of gut microbiota development. Since the gut microbiota is the primary driver of immune development, deviations from normal patterns of bacterial succession in early life can have long-term implications for immune functionality. There is a paucity of knowledge regarding how both iron deficiency and luminal iron availability affect gut microbiota development, or the subsequent impact on immunity, which are likely to be contributors to the increased risk of infection. Piglets are naturally iron deficient. This is largely due to their low iron endowments at birth (primarily due to large litter sizes), and their rapid growth combined with the low iron levels in sow milk. Thus, piglets consistently become iron deficient within days of birth which rapidly progresses to anemia in the absence of iron supplementation. Moreover, like humans, pigs are omnivorous and share many characteristics of human gut physiology, microbiota and immunity. In addition, their precocial nature permits early maternal separation, individual housing, and tight control of nutritional intake. Here, we highlight the advantages of piglets as valuable and highly relevant models for human infants in promoting understanding of how early iron status impacts physiological development. We also indicate how piglets offer potential to unravel the complexities of microbiota-immune responses during iron deficiency and in response to iron supplementation, and the link between these and increased risk of infectious disease.

Possible Effects of Early Maternal Separation on the Gut Microbiota of Captive Adult Giant Pandas.

Simple SummaryIn the process of ex-situ conservation, young giant pandas face a variety of unfavorable environmental impacts such as frequent maternal separation, parenting by non-parents, noise from tourists, and frequent replacement of animal houses, which may cause psychological and physiological stress. The gut microbiota is an important carrier of the interaction between the body and the environment, and recent studies revealed an association between stress and alterations of the intestinal microbiota. So, is the stress caused by the unfavorable parenting environment in the early life of captive giant pandas related to the gut microbiota? To answer this question, we use fecal metagenomics and LC-MS technology to study the effect of different parenting patterns on the structure, diversity, and metabolites of the intestinal microbial community of captive giant pandas. In order to evaluate the possible adverse effects of the traditional parenting mode on the gut microbiota of captive giant pandas in the early life, it can provide an important scientific basis for improving the welfare level of captive giant pandas.Maternal deprivation (MD) in early life induces dysbiosis in the host gut microbiota, which is a key determinant of abnormal behavior in stress model individuals. Compared with the early parenting environment of the wild, captive giant pandas face frequent and premature maternal separation. Will this lead to imbalance in intestinal flora and stress in captive giant pandas? The purpose of this research is to evaluate the possible adverse effects of the traditional parenting mode on the gut microbiota of captive giant pandas. The results showed that the frequent and premature maternal separation at early stages of the young did not change α and β diversity indices of the gut microbes, but it increased the relative abundance of s_Clostridium_tetani and s_Clostridium_sp_MSJ_8 (significantly positively correlated with the metabolism of propionic acid) and also the concentrations of fecal metabolites that are related to stress (N-acetyl-l-aspartic acid and corticosterone) in the intestinal tract of giant pandas in adulthood. Thereby, the function of protein digestion and absorption in the intestines of captive giant pandas was decreased, and the metabolism of short-chain fatty acids was disturbed. In conclusion, the parenting experience of early maternal separation could adversely affect the stress caused by the unfavorable parenting environment in the early life of captive giant pandas related to the gut microbiota of the captive giant pandas in adulthood.

Early life maternal separation induces sex-specific antidepressant-like responses but has minimal effects on adult stress susceptibility in mice.

Early life stress is known to increase the risk of depression and anxiety disorders, which are highly prevalent conditions that disproportionately affect women. However, the results of preclinical studies have been mixed, with some work suggesting that early life stress promotes anxiety-like behavior and/or increases susceptibility to subsequent stressors, and other research suggesting that early life stress reduces anxiety-like behavior and/or confers resilience to subsequent stress exposure. It is likely that factors such as sex and the timing and severity of early life and adult stress exposure dictate whether a particular early life experience promotes adaptive vs. maladaptive behavior later in life. Most work in this area has focused exclusively on males, but several sex differences in the effects of early life stress on subsequent stress susceptibility have been reported. The current study examined the impact of early life maternal separation on susceptibility to behavioral alterations induced by 3 days of variable stress in adulthood in male and female c57BL6 mice. Our results indicate that 3 days of adult stress is sufficient to increase anxiety-like behavior in several paradigms and to increase immobility in the forced swim test. In contrast, a history of maternal separation reduces anxiety-like behavior in several tests, particularly in males. These findings could contribute to our understanding of sex differences in mental illness by demonstrating that males are more likely than females to display adaptive responses to mild early life stressors.

Influence of early maternal separation on susceptibility to the activity-based anorexia model in male and female Sprague Dawley rats

A principal animal paradigm employed in Anorexia Nervosa (AN) study is the activity-based anorexia (ABA) model. The model's efficacy in recapitulating the core features of AN in humans allows for the study of the parameters involved in the disorder. The current study examined the susceptibility to the ABA protocol in the presence of a significant stressor (maternal separation) in male and female Sprague Dawley rats. More importantly, we analysed the sex-differences on activity levels during different periods of the ABA protocol to determine the period(s) influencing the most pathological weight loss. Both components of the ABA protocol contributed to the subjects’ bodyweight loss. Stress in the first two weeks of development conferred a protective effect in males. Time spent and activity levels on the running wheel were higher in females compared to males. Hyperactivity in ABA subjects was observed during the food-anticipatory activity (FAA) and postprandial activity in males and during the FAA and nocturnal activity periods in females. This study aids in understanding the effect of intensity of activity during specific periods on the pathological weight loss in ABA rats. These observations are informative for therapies aimed at ameliorating body mass index in AN patients.

A meta-analytic study of the effects of early maternal separation on cognitive flexibility in rodent offspring

Adverse early life experiences, such as maternal separation, are associated with an increased risk for several mental health problems. Symptoms induced by maternal separation that mirror clinically relevant aspects of mental problems, such as cognitive inflexibility, open the possibility of testing putative therapeutics prior to clinical development. Although several animal (e.g., rodent) studies have evaluated the effects of early maternal separation on cognitive flexibility, no consistent conclusions have been drawn. To clarify this issue, in this study, a meta-analysis method was used to systematically explore the relationship between early maternal separation and cognitive flexibility in rodent offspring. Results indicate that early maternal separation could significantly impair cognitive flexibility in rodent offspring. Moderator analyses further showed that the relationship between early maternal separation and cognitive flexibility was not consistent in any case, but was moderated by variations in the experimental procedures, such as the deprivation levels, task characteristics, and rodent strains. These clarify the inconsistent effects of maternal separation on cognitive flexibility in rodents and help us better understand the association between early life adversity and cognitive development.

Role of an enriched environment in ameliorating early life stress-induced changes in structure and functions of hippocampus and amygdala in rats

Objectives: This study aimed to understand whether an enriched environment (EE) in adulthood benefits in mitigating the early life stress-induced changes in the structure and functions of the hippocampus and amygdala. Materials and Methods: Male Wistar rats were exposed daily for 6 h to early maternal separation and isolation (MS) stress from postnatal days (PND) 4–14 and later at PND 60–70 days subjected to EE, while, the normal control (NC) rats were not subjected to stress but reared with the mother under standard housing conditions. The effects of MS and EE on adulthood behaviour were not subjected to stress but assessed by measuring the ambulatory, repetitive and anxiety-like behaviour. The study has also done the plasma corticosterone concentrations. The dendritic remodelling in the amygdala and hippocampus was assessed using the Golgi cox staining approach. Finally, the present study compared the reactive oxygen species-induced lipid peroxidation and total antioxidant capacity in MS rats as an indirect measure of oxidative stress to study the impact of MS stress on the limbic circuit and peripheral organs. Results: MS rats showed increased anxiety and lower plasma corticosterone levels. The pyramidal neurons’ dendritic plasticity displayed a different pattern, with shrinkage in the CA1 hippocampal neurons and hypertrophy in the amygdala’s primary neurons. Variations in antioxidant activity and peroxidation observed in NC to MS across tissues indicate the occurrence and management of oxidative stress in MS. The 10 days of EE in young adulthood helped to reduce MS stress-induced structural abnormalities in hippocampal and amygdala pyramidal neurons, as well as anxiety and plasma corticosterone levels. Conclusion: These findings together indicate that exposure to adverse experiences may cause harmful effects on brain plasticity and behaviour in young adulthood. Exposure to EE may be beneficial in reducing the early life stress-induced pathophysiology later in life.

Maternal Separation Alters Ethanol Drinking and Reversal Learning Processes in Adolescent Rats: The Impact of Sex and Glycine Transporter Type 1 (GlyT1) Inhibitor.

Adverse early life experiences are associated with an enhanced risk for mental and physical health problems, including substance abuse. Despite clinical evidence, the mechanisms underlying these relationships are not fully understood. Maternal separation (MS) is a commonly used animal model of early neglect. The aim of the current study is to determine whether the N-methyl-D-aspartate receptor (NMDAR)/glycine sites are involved in vulnerability to alcohol consumption (two-bottle choice paradigm) and reversal learning deficits (Barnes maze task) in adolescent rats subjected to the MS procedure and whether these effects are sex dependent. By using ELISA, we evaluated MS-induced changes in the NMDAR subunits (GluN1, GluN2A, GluN2B) expression, especially in the glycine-binding subunit, GluN1, in the prefrontal cortex (PFC) and ventral striatum (vSTR) of male/female rats. Next, we investigated whether Org 24598, a glycine transporter 1 (GlyT1) inhibitor, was able to modify ethanol drinking in adolescent and adult male/female rats with prior MS experience and reversal learning in the Barnes maze task. Our findings revealed that adolescent MS female rats consumed more alcohol which may be associated with a substantial increase in GluN1 subunit of NMDAR in the PFC and vSTR. Org 24598 decreased ethanol intake in both sexes with a more pronounced decrease in ethanol consumption in adolescent female rats. Furthermore, MS showed deficits in reversal learning in both sexes. Org 24598 ameliorated reversal learning deficits, and this effect was reversed by the NMDAR/glycine site inhibitor, L-701,324. Collectively, our results suggest that NMDAR/glycine sites might be targeted in the treatment of alcohol abuse in adolescents with early MS, especially females.

IDF21-0029 Maternal separation aggravated pancreatic oxidative and inflammatory damage in chronic socially defeated adult male rats

Background: It is believed that psychosocial stress as one of the main sources of stress in humans may play an essential role in developing chronic degenerative metabolic diseases. Early life adverse experiences were supposed to affect the response to stress in later life. Aim: This research was done to test the effect of maternal separation on the metabolic response to chronic social defeat stress (CSDS) at young adulthood. In this respect, the possible contribution of oxidative stress and inflammatory damage to the pancreas along with insulin resistance in response to CSDS exposure in young adult male rats who experienced early life maternal separation was explored. Method: During the first 2 weeks of life, male Wistar rats were exposed to either maternal separation (MS) or left undisturbed with their mothers (Std). Starting on postnatal date 50, the animals of each group were either left undisturbed in the standard group housing (Con) or underwent chronic social defeat stress (CSDS) for 3 weeks. Thus, totally there were 4 groups (n=6/group). Then, fasting plasma corticosterone, insulin, and glucose levels were measured and insulin resistance was calculated. Pancreatic Catalase (CAT) activity, reduced Glutathione (GSH), Malondialdehyde (MDA) and interleukin-1 beta contents were measured. Results: In this study, MS-CSDS animals showed an elevated fasting plasma corticosterone and insulin levels along with insulin resistance in comparison with standard-reared controls (Std-Con); however, neither early nor adult life adversity affected fasting glucose levels. Likewise, CAT activity, MDA, and Il-1β contents of pancreatic tissue were increased only in MS-CSDS rats compared to Std-Cons. Discussion: The finding of this study shows that maternal separation intensifies vulnerability to develop HPA axis over-activation, insulin resistance, pancreatic oxidative and inflammatory damage associated with chronic exposure to social defeat stress in young adult male rats, which could play an important role in mediating the effects of chronic stress‐related risk of diabetes mellitus. Abnormal responses to stress in adults, who were exposed to stress in early life, almost occurred because of increasing basal tone of central CRFergic activity and coincident intensified HPA axis responsiveness. It may be secondary to facilitation of noradrenergic neurocircuits, central glucocorticoid resistance, and/or dampened regional GABAergic tone that have been observed to happen in response to maternal separation stress. Elevated levels of circulating glucocorticoid have been reported to influence the insulin signaling cascade at the level of insulin receptor and insulin-sensitive glucose transporter 4 (GLUT4) functionality, which may contribute to insulin resistance. In the face of insulin resistance, the β cells adapt by increasing insulin secretion, leading to peripheral compensatory hyperinsulinemia as a protective measure to maintain normal glucose concentrations without hypoglycemia. Augmented pancreatic oxidative stress in MS-CSDS animals may exceeded the increased compensatory antioxidant mechanisms, as evidenced by excessive peroxidation of cell membrane lipids. Based on the central role of IL-1β in the destruction of pancreatic β cells, raised pancreatic IL-1β content could be related to oxidative stress-mediated β cell damage and development of diabetes in response to CSDS exposure in young adult rats who underwent early life maternal separation.

Epigenetic Mechanism of 5-HT/NE/DA Triple Reuptake Inhibitor on Adult Depression Susceptibility in Early Stress Mice.

Major depressive disorder (MDD) is a chronic, remitting and debilitating disease and the etiology of MDD is highly complicated that involves genetic and environmental interactions. Despite many pharmacotherapeutic options, many patients remain poorly treated and the development of effective treatments remains a high priority in the field. LPM570065 is a potent 5-hydroxytryptamine (5-HT), norepinephrine (NE) and dopamine (DA) triple reuptake inhibitor and both preclinical and clinical results demonstrate significant efficacy against MDD. This study extends previous findings to examine the effects and underlying mechanisms of LPM570065 on stress vulnerability using a “two-hit” stress mouse model. The “two-hit” stress model used adult mice that had experienced early life maternal separation (MS) stress for social defeat stress (SDS) and then they were evaluated in three behavioral assays: sucrose preference test, tail suspension test and forced swimming test. For the mechanistic studies, methylation-specific differentially expressed genes in mouse hippocampal tissue and ventral tegmental area (VTA) were analyzed by whole-genome transcriptome analysis along with next-generation bisulfite sequencing analysis, followed by RT-PCR and pyrophosphate sequencing to confirm gene expression and methylation. LPM570065 significantly reversed depressive-like behaviors in the mice in the sucrose preference test, the tail suspension test, and the forced swimming test. Morphologically, LPM570065 increased the density of dendritic spines in hippocampal CA1 neurons. Hypermethylation and downregulation of oxytocin receptor (Oxtr) in the hippocampal tissues along with increased protein expression of Dnmt1 and Dnmt3a in mice that experienced the “two-hit” stress compared to those that only experienced adulthood social defeat stress, and LPM570065 could reverse these changes. Combined, these results suggest that methylation specificity of the gene Oxtr in the hippocampus may play an important role in early life stress-induced susceptibility to depression and that the5-HT/NE/DA triple reuptake inhibitor LPM570065 may reduce depression susceptibility via the reversal of the methylation of the gene Oxtr.

Early maternal separation alters the activation of stress-responsive brain areas in adulthood

The expression of c-Fos protein has been extensively used as a marker of neuronal activation in response to stressful stimuli. Early maternal separation (MS) is a model of early life adversity that affects the responsiveness of the brain areas to stressors. Thus, this study examined the impact of early MS on activating stress-responsive areas in the brain of adult rats in response to physical (ether) or psychological (restraint) stressors. Male pups were divided for the MS or non-handled (NH) groups. The MS was carried out daily between the 2nd and 14th day of postnatal life and consisted in removing the dams from the cage for 180 min. The rats were then subjected to experimental protocols of restraint or ether exposure at 10–12 weeks old. The rats were anesthetized 90 min after exposure to the stressors, and their brains were prepared for immunohistochemical analysis of c-Fos immunoreactive (c-Fos-ir) neurons in the hypothalamic paraventricular nucleus (PVN), supraoptic nucleus (SON), medial preoptic area (MPA), medial amygdaloid nucleus (MeA), locus coeruleus (LC), and nucleus of the solitary tract (NST). The MS-group presented 86%, 125%, 73%, 56%, and 137% higher c-Fos-ir neurons in the LC, PVN, SON, MPA, and MeA, respectively, compared to NH-group in response to the restraint stressor. In addition, the MS-group presented 180%, 137%, 170%, and 138% higher c-Fos-ir neurons for the ether exposure in the LC, PVN, MPA, and MeA, respectively. Our results show a greater increase in neuronal activation in the MS group, indicating that early life adversity can induce reprogramming in the brain response to stress in adulthood.

Early life stress-induced neuroinflammation and neurological disorders: a novel perspective for research.

Early life stress-induced neuroinflammation and neurological disorders: a novel perspective for research.

Different Types of Environmental Stressors Could Have Disruptive or Constructive Effects on Vestibular Compensation

Background and Aim: Stress could play either helpful or harmful roles in vestibular compensation, the process of recovery after vestibular system lesions. Herein, we examined the effect of two stressor types on vestibular compensation: chronic anxiety disorder induced by early maternal separation (MS), and caloric restriction by an intermittent fasting (IF) diet. Methods: Male Wistar rats (n=56) received maternal separation (the MS group), intermittent fasting (IF group), unilateral vestibular deafferentation (UVD group), or a mixture of these interventions (UVD+IF, UVD+MS, and UVD+IF+MS). All the groups were compared with control animals. The animals’ balance, motor coordination, anxiety, locomotor activity, and serum cortisol levels were evaluated by rotarod, open field, and enzyme-linked immunosorbent assay methods, respectively. The data were compared with those of the healthy control (HC) group. Results: The UVD animals did not show a significant change in the time on the rod, except for the IF+UVD group (p=0.04). There was no significant difference between the experimental groups on the open field indices, except for the MS+IF+UVD group which traveled a significantly less total distance (p=0.02). Serum cortisol levels were significantly higher than HCs for all the groups except for the sham saline and IF+UVD group (p&lt;0.05). Conclusion: IF seems to promote compensation after UVD, while MS may disrupt it. However, IF loses its beneficial outcomes if the animal has received another source of stress, i.e. MS.

Early maternal separation enhances melanoma progression in adult female mice by immune mechanisms

Maternal separation (MS) is a risk factor for major depressive disorder. Both cancer and depression seem to share a common biological link. Here, we evaluated the progression of melanoma and the underlying mechanisms related to this progression, namely cell proliferation and apoptosis, in adult female mice exposed to MS. Female C57BL/6 mice were exposed to MS for 60 min/day during the first 2 postnatal weeks (here called MS mice) or left undisturbed (here called non-MS mice). Melanoma cells were inoculated subcutaneously into the axillary region of adult animals, and tumor progression was evaluated for 25 days. Adult MS mice presented depressive-like behavior and working memory deficits. MS accelerated murine melanoma growth by mechanisms related to decreased apoptosis and increased cell proliferation rate, such as increased expression of IL-6 and mTOR. MS stimulated eukaryotic elongation factor 2 expression and increased the number of circulating monocytes and DNA damage in peripheral blood leukocytes, an effect associated with oxidative DNA damage. In conclusion, MS accelerated the progression of murine melanoma by mechanisms related to tumor proliferation and apoptosis, revealing a relationship between adverse childhood experiences and cancer progression, particularly melanoma.