Early life genetic, epigenetic and environmental factors shaping emotionality in rodents

Long-term impacts of prenatal maternal immune activation and postnatal maternal separation on maternal behavior in adult female rats: Relevance to postpartum mental disorders

Early life adversities are known to exert long-term negative impacts on psychological and brain functions in adulthood. The present work examined how a prenatal brain insult and a postnatal stressor independently or interactively influence the quality of maternal care of postpartum female rats and their cognitive and emotional functions, as a way to identify the behavioral dysfunctions underlying childhood trauma-induced postpartum mental disorders (as indexed by impaired maternal care). Sprague-Dawley female offspring born from mother rats exposed to polyinosinic:polycytidylic acid (PolyI:C, 4.0-6.0 mg/kg) intended to cause gestational maternal immune activation (MIA) or saline were subjected to a repeated maternal separation stress (RMS, 3 h/day) or no separation for 9 days in the first two weeks of life (a 2 × 2 design). When these offspring became mothers, their attentional filtering ability (as measured in the prepulse inhibition of acoustic startle reflex test), positive hedonic response (as measured in the sucrose preference test), and negative emotional response (as measured in the startle reflex and fear-potentiated startle test) were examined, along with their home-cage maternal behavior. Virgin littermates served as controls in all the behavioral tests except in maternal behavior. Results showed that mother rats who experienced RMS displayed impaired nest building and crouching/nursing activities. RMS also interacted with MIA to alter pup retrieval latency and startle reactivity, such that MIA-RMS dams demonstrated significantly slower pup retrieval latency and higher startle magnitude compared to either RMS-only and MIA-only mothers. MIA also disrupted attentional filtering ability, with significantly lower prepulse inhibition. However, neither prenatal MIA nor postnatal RMS impaired sucrose preference or the acquisition of fear-potentiated startle. These results indicate that prenatal stress and postnatal adversity could impair maternal behavior individually, and interact with each other, causing impairments in attention, emotion and maternal motivation.

Early parental deprivation during primate infancy has a lifelong impact on gene expression in the male marmoset brain

Adverse early life experiences are well-established risk factors for neurological disorders later in life. However, the molecular mechanisms underlying the impact of adverse experiences on neurophysiological systems throughout life remain incompletely understood. Previous studies suggest that social attachment to parents in early development are indispensable for infants to grow into healthy adults. In situations where multiple offspring are born in a single birth in common marmosets, human hand-rearing is employed to ensure the survival of the offspring in captivity. However, hand-reared marmosets often exhibit behavioral abnormalities, including abnormal vocalizations, excessive attachment to the caretaker, and aggressive behavior. In this study, comprehensive transcriptome analyses were conducted on hippocampus tissues, a neuroanatomical region sensitive to social attachment, obtained from human hand-reared (N = 6) and parent-reared male marmosets (N = 5) at distinct developmental stages. Our analyses revealed consistent alterations in a subset of genes, including those related to neurodevelopmental diseases, across different developmental stages, indicating their continuous susceptibility to the effects of early parental deprivation. These findings highlight the dynamic nature of gene expression in response to early life experiences and suggest that the impact of early parental deprivation on gene expression may vary across different stages of development.

Shaping the development of complex social behavior

Early life experiences can have an enduring impact on the brain and behavior, with implications for stress reactivity, cognition, and social behavior. In particular, the neural systems that contribute to the expression of social behavior are altered by early life social environments. However, paradigms that have been used to alter the social environment during development have typically focused on exposure to stress, adversity, and deprivation of species-typical social stimulation. Here, we explore whether complex social environments can shape the development of complex social behavior. We describe lab-based paradigms for studying early life social complexity in rodents that are generally focused on enriching the social and sensory experiences of the neonatal and juvenile periods of development. The impact of these experiences on social behavior and neuroplasticity is highlighted. Finally, we discuss the degree to which our current approaches for studying social behavior outcomes give insight into "complex" social behavior and how social complexity can be better integrated into lab-based methodologies.

Perceptual learning deficits mediated by somatostatin releasing inhibitory interneurons of olfactory bulb in an early life stress mouse model

Early life adversity (ELA) causes aberrant functioning of neural circuits affecting the health of an individual. While ELA-induced behavioural disorders resulting from sensory and cognitive disabilities can be assessed clinically, the neural mechanisms need to be probed using animal models by employing multi-pronged experimental approaches. As ELA can alter sensory perception, we investigated the effect of early weaning on murine olfaction. By implementing go/no-go odour discrimination paradigm, we observed olfactory learning and memory impairments in early life stressed (ELS) male mice. As olfactory bulb (OB) circuitry plays a critical role in odour learning, we studied the plausible changes in the OB of ELS mice. Lowered c-Fos activity in the external plexiform layer and a reduction in the number of dendritic processes of somatostatin-releasing, GABAergic interneurons (SOM-INs) in the ELS mice led us to hypothesise the underlying circuit. We recorded reduced synaptic inhibitory feedback on mitral/tufted (M/T) cells, in the OB slices from ELS mice, explaining the learning deficiency caused by compromised refinement of OB output. The reduction in synaptic inhibition was nullified by the photo-activation of ChR2-expressing SOM-INs in ELS mice. The role of SOM-INs was revealed by learning-dependent refinement of Ca2+dynamics quantified by GCaMP6f signals, which was absent in ELS mice. Further, the causal role of SOM-INs involving circuitry was investigated by optogenetic modulation during the odour discrimination learning. Photo-activating these neurons rescued the ELA-induced learning deficits. Conversely, photo-inhibition caused learning deficiency in control animals, while it completely abolished the learning in ELS mice, confirming the adverse effects mediated by SOM-INs. Our results thus establish the role of specific inhibitory circuit in pre-cortical sensory area in orchestrating ELA-dependent changes.

Inhibition of xCT by sulfasalazine alleviates the depression-like behavior of adult male mice subjected to maternal separation stress

Maternal separation (MS) can induce emotional disorders. Our previous study reported that MS resulted in depression-like behavior. In this study, we aimed to explore the role of xCT in depression-like behavior in adult mice subjected to MS stress. Pups were divided into the control group, the control + sulfasalazine (SSZ, 75 mg/kg/day, i.p.) group, the MS group, and the MS+SSZ group. After MS, all pups were raised until PD60. Then, the depression-like behavior was detected by the novelty suppressed feeding (NSF) test, the forced swimming test (FST), and the tail suspension test (TST). The synaptic plasticity was examined by electrophysiological recordings and molecular biotechnology. The data showed that, compared with the control group, the mice in the MS group presented depression-like behavior, impairment of long-term potentiation (LTP), a reduction in the number of astrocytes, and activation of the microglia. Moreover, the expression of xCT was increased in the prefrontal cortex of MS mice, the EAAT2 and the Group Ⅱ metabotropic glutamate receptors (mGluR2/3) were decreased, and the level of pro-inflammatory factors was increased in the prefrontal cortex. After the administration with SSZ, the depression-like behavior and the impairment of LTP were alleviated, the number of astrocytes was increased, and the microglial activation was inhibited. Moreover, the levels of EAAT2 and mGluR2/3 were ameliorated, the over-activation of the microglia was mitigated, and the levels of glutamate and pro-inflammatory factors were decreased. In conclusion, the inhibition of xCT by SSZ could alleviate depression-like behavior partly via modulating the homeostasis of the glutamate system and dampening neuroinflammation.

Lasting impact of postnatal maternal separation on the developing BNST: Lifelong socioemotional consequences

Nearly one percent of children in the US experience childhood neglect or abuse, which can incite lifelong emotional and behavioral disorders. Many studies investigating the neural underpinnings of maleffects inflicted by early life stress have largely focused on dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Newer veins of evidence suggest that exposure to early life stressors can interrupt neural development in extrahypothalamic areas as well, including the bed nucleus of the stria terminalis (BNST). One widely used approach in this area is rodent maternal separation (MS), which typically consists of separating pups from the dam for extended periods of time, over several days during the first weeks of postnatal life - a time when pups are highly dependent on maternal care for survival. MS has been shown to incite myriad lasting effects not limited to increased anxiety-like behavior, hyper-responsiveness to stressors, and social behavior deficits. The behavioral effects of MS are widespread and thus unlikely to be limited to hypothalamic mechanisms. Recent work has highlighted the BNST as a critical arbiter of some of the consequences of MS, especially socioemotional behavioral deficits. The BNST is a well-documented modulator of anxiety, reward, and social behavior by way of its connections with hypothalamic and extra-hypothalamic systems. Moreover, during the postnatal period when MS is typically administered, the BNST undergoes critical neural developmental events. This review highlights evidence that MS interferes with neural development to permanently alter BNST circuitry, which may account for a variety of behavioral deficits seen following early life stress. This article is part of the Special Issue on 'Fear, Anxiety and PTSD'.

Sex-dependent worsening of NMDA-induced responses, anxiety, hypercortisolemia, and organometry of early peripheral immunoendocrine impairment in adult 3xTg-AD mice and their long-lasting ontogenic modulation by neonatal handling

The neuroimmunomodulation hypothesis for Alzheimer's disease (AD) postulates that alterations in the innate immune system triggered by damage signals result in adverse effects on neuronal functions. The peripheral immune system and neuroimmunoendocrine communication are also impaired. Here we provide further evidence using a longitudinal design that also studied the long-lasting effects of an early life sensorial intervention (neonatal handling, from postnatal day 1-21) in 6-month-old (early stages of the disease) male and female 3xTg-AD mice compared to age- and sex-matched non-transgenic (NTg) mice with normal aging. The behavioral patterns elicited by the direct exposure to an open field, and the motor depression response evoked by NMDA (25 mg/kg, i.p) were found correlated to the organometry of peripheral immune-endocrine organs (thymus involution, splenomegaly, and adrenal glands' hypertrophy) and increased corticosterone levels, suggesting their potential value for diagnostic and biomonitoring.The NMDA-induced immediate and depressant motor activity and endocrine (corticosterone) responses were sensitive to sex and AD-genotype, suggesting worse endogenous susceptibility/neuroprotective response to glutamatergic excitotoxicity in males and in the AD-genotype. 3xTg-AD females showed a reduced immediate response, whereas the NTg showed higher responsiveness to subsequent NMDA-induced depressant effect than their male counterparts. The long-lasting ontogenic modulation by handling was shown as a potentiation of NMDA-depressant effect in NTg males and females, while sex × treatment effects were found in 3xTg-AD mice. Finally, NMDA-induced corticosterone showed sex, genotype and interaction effects with sexual dimorphism enhanced in the AD-genotype, suggesting different endogenous vulnerability/neuroprotective capacities and modulation of the neuroimmunoendocrine system.

Postpartum depression in rats causes poor maternal care and neurochemical alterations on dams and long-lasting impairment in sociability on the offspring

Postpartum depression is a mentally disabling disease with multifactorial etiology that affects women worldwide. It can also influence child development and lead to behavioral and cognitive alterations. Despite the high prevalence, the disease is underdiagnosed and poorly studied. To study the postpartum depression caused by maternal separation model in rats, dams were separated from their litter for 3 h daily starting from lactating day (LD) 2 through LD12. Maternal studies were conducted from LD5 to LD21 and the offspring studies from postnatal day (PND) 2 through PND90. The stress caused by the dam-offspring separation led to poor maternal care and a transient increase in anxiety in the offspring detected during infancy. The female offspring also exhibited a permanent impairment in sociability during adult life. These changes were associated with neurochemical alterations in the prefrontal cortex and hippocampus, and low TSH concentrations in the dams, and in the hypothalamus, hippocampus and striatum of the offspring. These results indicate that the postpartum depression resulted in a depressive phenotype, changes in the brain neurochemistry and in thyroid economy that remained until the end of lactation. Changes observed in the offspring were long-lasting and resemble what is observed in children of depressant mothers.

Limited bedding nesting paradigm alters maternal behavior and pup's early developmental milestones but did not induce anxiety- or depressive-like behavior in two different inbred mice

Animal models are crucial to understanding the mechanisms underlying the deleterious consequences of early-life stress. Here, we aimed to examine the effect of the limited bedding nesting (LBN) paradigm on early life development milestones and anxiety- and/or depression-like behavior in adolescent and adult mice from two inbred mice of both sexes. C57BL/6NCrl and BALB/c litters were exposed to the LBN paradigm postnatal day (PND) 2-9. Maternal behavior recording occurred on PND 3-9, and pups were weighed daily and examined to verify the eye-opening on PND 10-22. The male and female offspring underwent evaluation in the open field test, elevated plus-maze, and the forced swimming test during adolescence (PND 45-49) and adulthood (PND 75-79). We found that LBN impaired the maternal behavior patterns of both strain dams, mainly on C57BL/6NCrl strain. Also, LBN delayed the pup's eye-opening time and reduced body weight gain, impacting C57BL/6NCrl pups more. We also found that LBN decreased anxiety-related indices in adolescent and adult male but not female mice of both strains. Furthermore, LBN decreased depression-related indices only adolescent female and male BALB/c and female but not male C57BL/6NCrl mice. These findings reinforce the evidence that the LBN paradigm impairs the maternal behavior pattern and pup's early developmental milestones but does not induce anxiety- or depressive-like behavior outcomes during later life.

Comparison of LPS and MS-induced depressive mouse model: behavior, inflammation and biochemical changes

Depression is a mental disease involving complex pathophysiological mechanisms, and there are many ways to establish depressive mouse models. The purpose of this study is to comprehensively compare the behavioral changes and its mechanism induced by two different models. This study established two depressive mouse models by maternal separation (MS) or lipopolysaccharide (LPS) administration, and added fluoxetine treatment group respectively for comparison. MS induced more apparent anxiety-like behavior while LPS induced more apparent depressive-like behavior. LPS increased peripheral inflammatory factors more apparent, which were mitigated by fluoxetine. MS inhibited the 5-HT system more obviously and was relieved by fluoxetine. LPS triggered stronger immune response in the hippocampus and prefrontal cortex (PFC). MS significantly reduced the expression of neurotrophic proteins and was alleviated by fluoxetine. Overall, LPS induced stronger system inflammation, while MS impaired the function of HPA axis and 5-HT system. Our results will contribute to a deeper understanding of the pathophysiology of different stress-induced depression and will also help researchers select appropriate models of depression for their own needs.

Early Life Adversity and Neuropsychiatric Disease: Differential Outcomes and Translational Relevance of Rodent Models

It is now well-established that early life adversity (ELA) predisposes individuals to develop several neuropsychiatric conditions, including anxiety disorders, and major depressive disorder. However, ELA is a very broad term, encompassing multiple types of negative childhood experiences, including physical, sexual and emotional abuse, physical and emotional neglect, as well as trauma associated with chronic illness, family separation, natural disasters, accidents, and witnessing a violent crime. Emerging literature suggests that in humans, different types of adverse experiences are more or less likely to produce susceptibilities to certain conditions that involve affective dysfunction. To investigate the driving mechanisms underlying the connection between experience and subsequent disease, neuroscientists have developed several rodent models of ELA, including pain exposure, maternal deprivation, and limited resources. These studies have also shown that different types of ELA paradigms produce different but somewhat overlapping behavioral phenotypes. In this review, we first investigate the types of ELA that may be driving different neuropsychiatric outcomes and brain changes in humans. We next evaluate whether rodent models of ELA can provide translationally relevant information regarding links between specific types of experience and changes in neural circuits underlying dysfunction.

Natural products for the treatment of stress-induced depression: Pharmacology, mechanism and traditional use

ETHNOPHARMACOLOGICAL RELEVANCE

Depression, one of the most common psychiatric disorders, is the fourth leading cause of long-term disability worldwide. A series of causes triggered depression, including psychological stress and conflict, as well as biological derangement, among which stress has a pivotal role in the development of depression. Traditional herbal medicine has been used for the treatment of various disorders including depression for a long history with multi-targets, multi-levels and multi-ways, attracting great attention from scholars. Recently, natural products have been commercialized as antidepressants which have become increasingly popular in the world health drug markets. Major research contributions in ethnopharmacology have generated and updated vast amount of data associated with natural products in antidepressant-like activity.

AIMS OF THE REVIEW

This review aims to briefly discuss the pathological mechanism, animal models of stress-induced depression, traditional use of herbal medicines and especially recapitulate the natural products with antidepressant activity and their pharmacological functions and mechanism of action, which may contribute to a better understanding of potential therapeutic effects of natural products and the development of promising drugs with high efficacy and low toxicity for the treatment of stress-induced depression.

MATERIALS AND METHODS

The contents of this review were sourced from electronic databases including PubMed, Sci Finder, Web of Science, Science Direct, Elsevier, Google Scholar, Chinese Knowledge On frastructure (CNKI), Wan Fang, Chinese Scientific and Technological Periodical Database (VIP) and Chinese Biomedical Database (CBM). Additional information was collected from Yao Zhi website (https://db.yaozh.com/). Data were obtained from April 1992 to June 2021. Only English language was applied to the search. The search terms were 'stress-induced depression', 'pathological mechanism' in the title and 'stress', 'depression', 'animal model' and 'natural products' in the whole text.

RESULTS

Stress-induced depression is related to the monoaminergic system, hypothalamic-pituitary-adrenal (HPA) axis, neuronal plasticity and a series of inflammatory factors. Four main types of animal models of stress-induced depression were represented. Fifty-eight bioactive phytochemical compounds, fifty-six herb medicines and five formulas from traditional Chinese medicine were highlighted, which exert antidepressant effects by inhibiting monoamine oxidase (MAO) reaction, alleviating dysfunction of the HPA axis and nerve injury, and possessing anti-inflammatory activities.

CONCLUSIONS

Natural products provide a large number of compounds with antidepressant-like effects, and their therapeutic impacts has been highlighted for a long time. This review summarized the pathological mechanism and animal models of stress-induced depression, and the natural products with antidepressant activity in particular, which will shed light on the action mechanism and clinical potential of these compounds. Natural products also have been a vital and promising source for future antidepressant drug discovery.

Family environment and development in children adopted from institutionalized care

BACKGROUND

After adoption, children exposed to institutionalized care show significant improvement, but incomplete recovery of growth and developmental milestones. There is a paucity of data regarding risk and protective factors in children adopted from institutionalized care. This prospective study followed children recently adopted from institutionalized care to investigate the relationship between family environment, executive function, and behavioral outcomes.

METHODS

Anthropometric measurements, physical examination, endocrine and bone age evaluations, neurocognitive testing, and behavioral questionnaires were evaluated over a 2-year period with children adopted from institutionalized care and non-adopted controls.

RESULTS

Adopted children had significant deficits in growth, cognitive, and developmental measurements compared to controls that improved; however, residual deficits remained. Family cohesiveness and expressiveness were protective influences, associated with less behavioral problems, while family conflict and greater emphasis on rules were associated with greater risk for executive dysfunction.

CONCLUSIONS

Our data suggest that a cohesive and expressive family environment moderated the effect of pre-adoption adversity on cognitive and behavioral development in toddlers, while family conflict and greater emphasis on rules were associated with greater risk for executive dysfunction. Early assessment of child temperament and parenting context may serve to optimize the fit between parenting style, family environment, and the child's development.

IMPACT

Children who experience institutionalized care are at increased risk for significant deficits in developmental, cognitive, and social functioning associated with a disruption in the development of the prefrontal cortex. Aspects of the family caregiving environment moderate the effect of early life social deprivation in children. Family cohesiveness and expressiveness were protective influences, while family conflict and greater emphasis on rules were associated with a greater risk for executive dysfunction problems. This study should be viewed as preliminary data to be referenced by larger studies investigating developmental and behavioral outcomes of children adopted from institutional care.

Lactobacillus reuteri effects on maternal separation stress in newborn mice

BACKGROUND

Probiotic Lactobacillus reuteri DSM 17938 (LR 17938) is beneficial to infants with colic. To understand its mechanism of action, we assessed ultrasonic vocalizations (USV) and brain pain/stress genes in newborn mice exposed to maternal separation stress.

METHODS

Pups were exposed to unpredictable maternal separation (MSU or SEP) or MSU combined with unpredictable maternal stress (MSU + MSUS or S + S), from postnatal days 5 to 14. USV calls and pain/stress/neuroinflammation-related genes in the brain were analyzed.

RESULTS

We defined 10 different neonatal call patterns, none of which increased after MSU. Stress reduced overall USV calls. Orally feeding LR 17938 also did not change USV calls after MSU. However, LR 17938 markedly increased vocalizations in mice allowed to stay with their dams. Even though LR 17938 did not change MSU-related calls, LR 17938 modulated brain genes related to stress and pain. Up-regulated genes following LR 17938 treatment were opioid peptides, kappa-opioid receptor 1 genes, and CD200, important in anti-inflammatory signaling. LR 17938 down-regulated CCR2 transcripts, a chemokine receptor, in the stressed neonatal brain.

CONCLUSIONS

USV calls in newborn mice are interpreted as "physiological calls" instead of "cries." Feeding LR 17938 after MSU did not change USV calls but modulated cerebral genes favoring pain and stress reduction and anti-inflammatory signaling.

IMPACT

We defined mouse ultrasonic vocalization (USV) call patterns in this study, which will be important in guiding future studies in other mouse strains. Newborn mice with maternal separation stress have reduced USVs, compared to newborn mice without stress, indicating USV calls may represent "physiological calling" instead of "crying." Oral feeding of probiotic Lactobacillus reuteri DSM 17938 raised the number of calls when newborn mice continued to suckle on their dams, but not when mice were under stress. The probiotic bacteria had a dampening effect on monocyte activation and on epinephrine and glutamate-related stress gene expression in the mouse brain.

The brain oxytocin and corticotropin-releasing factor systems in grieving mothers: What we know and what we need to learn

The bond between a mother and her child is the strongest bond in nature. Consequently, the loss of a child is one of the most stressful and traumatic life events that causes Prolonged Grief Disorder in up to 94 % of bereaved parents. While both parents are affected, mothers are of higher risk to develop mental health complications; yet, very little research has been done to understand the impact of the loss of a child, stillbirth and pregnancy loss on key neurobiological systems. The emotional impact of losing a child, e.g., Prolonged Grief Disorder, is likely accompanied by dysregulations in neural systems important for mental health. Among those are the neuropeptides contributing to attachment and stress processing. In this review, we present evidence for the involvement of the brain oxytocin (OXT) and corticotropin-releasing factor (CRF) systems, which both play a role in maternal behavior and the stress response, in the neurobiology of grief in mothers from a behavioral and molecular point of view. We will draw conclusions from reviewing relevant animal and human studies. However, the paucity of research on the tragic end to an integral bond in a female's life calls for the need and responsibility to conduct further studies on mothers experiencing the loss of a child both in the clinic and in appropriate animal models.

Paw preferences in mice and rats: Meta-analysis

Mice and rats are among the most common animal model species in both basic and clinical neuroscience. Despite their ubiquity as model species, many clinically relevant brain-behaviour relationships in rodents are not well understood. In particular, data on hemispheric asymmetries, an important organizational principle in the vertebrate brain, are conflicting as existing studies are often statistically underpowered due to small sample sizes. Paw preference is one of the most frequently investigated forms of hemispheric asymmetries on the behavioural level. Here, we used meta-analysis to statistically integrate findings on paw preferences in rats and mice. For both species, results indicate significant hemispheric asymmetries on the individual level. In mice, 81 % of animals showed a preference for either the left or the right paw, while 84 % of rats showed this preference. However, contrary to what has been reported in humans, population level asymmetries were not observed. These results are particularly significant as they point out that paying attention to potential individual hemispheric differences is important in both basic and clinical neuroscience.

Sex-dependent and ontogenetic effects of low dose ethanol on social behavioral deficits induced by mouse maternal separation

Early life stress can induce lifelong emotional and social behavioral deficits that may in some cases be alleviated by drugs or alcohol. A model for early life stress, rodent maternal separation, recapitulates these behavioral sequelae, which are not limited to potentiated anxiety-like behavior, attenuated social motivation, and altered reward-seeking. Here we employed mouse maternal separation with early weaning (MSEW), consisting of pup-dam separation lasting 4-8 hours on postnatal days (PD) 2-16, with early weaning on PD 17. Prior MSEW studies have limited subjects by age or sex, so we more comprehensively investigated MSEW effects in both sexes, during adolescence and adulthood. We found universal effects of MSEW to include lifelong enhancement of anxiety-like and despair behavior, as well as deficits in social motivation. We also observed some sex-dependent effects of MSEW, namely that female MSEW mice exhibited social habituation to a greater degree than their male counterparts. Low dose ethanol administration had no major effects on the social behavior of non-stressed mice. But interestingly, MSEW-induced social habituation was counteracted by low dose ethanol in adolescent female mice, and potentiated in adolescent male mice. These effects were absent in adult animals, suggesting that ethanol may exert differential effects on the developing brain in such a manner to produce age-, sex-, and stress-dependent effects upon social behavior. Together, results indicate that MSEW reliably produces long-lasting impairments in emotional and social behaviors in both sexes and across the lifespan, but may exert more salient social behavioral effects on female animals.

Serotonin deficiency induced after brain maturation rescues consequences of early life adversity

Brain serotonin (5-HT) system dysfunction is implicated in depressive disorders and acute depletion of 5-HT precursor tryptophan has frequently been used to model the influence of 5-HT deficiency on emotion regulation. Tamoxifen (TAM)-induced Cre/loxP-mediated inactivation of the tryptophan hydroxylase-2 gene (Tph2) was used to investigate the effects of provoked 5-HT deficiency in adult mice (Tph2 icKO) previously subjected to maternal separation (MS). The efficiency of Tph2 inactivation was validated by immunohistochemistry and HPLC. The impact of Tph2 icKO in interaction with MS stress (Tph2 icKO × MS) on physiological parameters, emotional behavior and expression of 5-HT system-related marker genes were assessed. Tph2 icKO mice displayed a significant reduction in 5-HT immunoreactive cells and 5-HT concentrations in the rostral raphe region within four weeks following TAM treatment. Tph2 icKO and MS differentially affected food and water intake, locomotor activity as well as panic-like escape behavior. Tph2 icKO prevented the adverse effects of MS stress and altered the expression of the genes previously linked to stress and emotionality. In conclusion, an experimental model was established to study the behavioral and neurobiological consequences of 5-HT deficiency in adulthood in interaction with early-life adversity potentially affecting brain development and the pathogenesis of depressive disorders.

Early life malnutrition and fluctuating asymmetry in the rat bony labyrinth

Maternal malnutrition during gestation and lactation is known to have adverse effects on offspring. We evaluate the impact of maternal diet on offspring bony labyrinth morphology. The bony labyrinth develops early and is thought to be stable to protect vital sensory organs within. For these reasons, bony labyrinth morphology has been used extensively to assess locomotion, hearing function, and phylogeny in primates and numerous other taxa. While variation related to these parameters has been documented, there is still a component of intraspecific variation that is unexplained. Although the labyrinthine developmental window is small, it may provide the opportunity for developmental instability to produce corresponding shape differences, as measured by fluctuating asymmetry (FA). We hypothesized that (a) offspring with poor maternal diet would exhibit increased FA, but (b) no unilateral shape difference. To test these hypotheses, we used two groups of rats (Rattus norvegicus; Crl:WI[Han] strain), one control group and one group exposed to a isocaloric, protein-restricted maternal diet during gestation and suckling. Individuals were sampled at weaning, sexual maturity, and old age. A Procrustes analysis of variance identified statistically significant FA in all diet-age subgroups. No differences in level of FA were identified among the subgroups, rejecting our first hypothesis. A principal components analysis identified no unilateral shape differences, supporting our second hypothesis. These results indicate that bony labyrinth morphology is remarkably stable and likely protected from a poor maternal diet during development. In light of this result, other factors must be explored to explain intraspecific variation in labyrinthine shape.

Maternal immune activation and repeated maternal separation alter offspring conditioned avoidance response learning and antipsychotic response in male rats

Previous work shows that repeated administration of several commonly used antipsychotic drugs, such as olanzapine (OLZ) over several days, induces an enhanced disruption of conditioned avoidance response (CAR) (termed antipsychotic sensitization) in normal adolescent and adult rats. However, it is unclear whether the same phenomenon can also be demonstrated in rat models of schizophrenia. The present study investigated OLZ sensitization in a combined maternal immune activation (MIA) and repeated maternal separation (RMS) model of schizophrenia. Sprague-Dawley male rats were first subjected to an early prenatal exposure to polyinosinic:polycytidylic acid (PolyI:C) on gestation days 13 (4 mg/kg, iv) and 15 (6 mg/kg, iv). They were then repeatedly separated from their mothers for 3 h daily during the first two weeks of postpartum. After they became adolescent (on postnatal day, PND 43), acute and OLZ sensitization effects in the CAR model was assessed. Adolescent MIA rats showed an impaired acquisition of conditioned avoidance response, but displayed a normal acute OLZ-induced avoidance suppression and OLZ sensitization effect. In adulthood (PND 81), MIA rats again showed an impairment in the acquisition of CAR. However, they showed a reduced response to OLZ (1.0 mg/kg; sc) treatment during the repeated drug test days, indicating a disruption of the induction of OLZ sensitization. In the OLZ sensitization challenge test, both MIA and control rats exhibited a robust and similar sensitization effect. In both adolescence and adulthood, RMS alone had no effect on any of the behavioral outcomes, and combined MIA-RMS even abolished the MIA alone-induced disruption of avoidance acquisition and the induction of OLZ sensitization. These results indicate that MIA disrupts associative learning and may reduce antipsychotic efficacy in the early stage of OLZ treatment. RMS does not appear to affect associative learning and behavioral responses to OLZ, and may possibly attenuate MIA-induced deficits. Our findings demonstrate that OLZ sensitization is a robust phenomenon but its magnitude can be altered by early MIA.

A cross-species assessment of behavioral flexibility in compulsive disorders

Lack of behavioral flexibility has been proposed as one underlying cause of compulsions, defined as repetitive behaviors performed through rigid rituals. However, experimental evidence has proven inconsistent across human and animal models of compulsive-like behavior. In the present study, applying a similarly-designed reversal learning task in two different species, which share a common symptom of compulsivity (human OCD patients and Sapap3 KO mice), we found no consistent link between compulsive behaviors and lack of behavioral flexibility. However, we showed that a distinct subgroup of compulsive individuals of both species exhibit a behavioral flexibility deficit in reversal learning. This deficit was not due to perseverative, rigid behaviors as commonly hypothesized, but rather due to an increase in response lability. These cross-species results highlight the necessity to consider the heterogeneity of cognitive deficits in compulsive disorders and call for reconsidering the role of behavioral flexibility in the aetiology of compulsive behaviors.

Early environmental enrichment and impoverishment differentially affect addiction-related behavioral traits, cocaine-taking, and dopamine D2/3 receptor signaling in a rat model of vulnerability to drug abuse

RATIONALE

Risk factors for drug addiction include genetics, environment, and behavioral traits such as impulsivity and novelty preference (NP), which have been related to deficits in striatal dopamine (DA) D_2/3-receptors (D_2/3R) and heightened amphetamine (AMPH)-induced DA release. However, the influence of the early rearing environment on these behavioral and neurochemical variables is not clear.

OBJECTIVES

We investigated the influence of early rearing environment on striatal D_2/3R availabilities and AMPH-induced DA release in relation to impulsivity, NP, and propensity to drug self-administration (SA) in "addiction-prone" Roman high- (RHA) and "addiction-resistant" Roman low-avoidance (RLA) rats.

METHODS

Animals were reared post-weaning in either environmental enrichment (EE) or impoverishment (EI) and were assessed at adulthood for impulsivity, NP, and propensity to cocaine SA. EE and EI rats were also scanned using single-photon emission computed tomography to concurrently measure in vivo striatal D_2/3R availability and AMPH-induced DA release.

RESULTS

EE vs. EI was associated with heightened impulsivity and a lack of NP in both rat lines. Higher dorsal striatal D_2/3R densities were found in RHA EE and higher AMPH-induced DA release in RLA EE. Both impulsivity and NP were negatively correlated to dorsal striatal D_2/3R availabilities and positively correlated with AMPH-induced DA release in EI but not in EE. EE vs. EI was related to a faster rate of cocaine intake and elevated active timeout responses in RHAs.

CONCLUSION

Our results suggest non-monotonic, environment-dependent, relationships between impulsivity, NP, and D_2/3R-mediated signaling, and suggest that EI vs. EE may decrease the reinforcing effects of psychostimulants in predisposed individuals.

A novel mouse model for vulnerability to alcohol dependence induced by early-life adversity

Childhood adversity increases vulnerability to alcohol use disorders and preclinical models are needed to investigate the underlying neurobiological mechanisms. The present study modeled early-life adversity by rearing male and female C57BL/6J mouse pups in a limited bedding and nesting (LBN) environment, which induces erratic maternal care. As adults, mice were given limited access to two-bottle choice (2BC) alcohol drinking, combined or not with chronic intermittent ethanol (CIE) vapor inhalation to induce alcohol dependence. We tested the hypothesis that LBN rearing might exacerbate or facilitate the emergence of the motivational and affective effects of CIE. Consistent with our hypothesis, although LBN-reared males consumed the same baseline levels of alcohol as controls, they escalated their ethanol intake at an earlier stage of CIE exposure, i.e., after 4 rounds vs. 5 rounds for controls. In contrast, females were insensitive to both LBN rearing and CIE exposure. Males were further subjected to a behavioral test battery. Withdrawal from CIE-2BC increased digging activity and lowered mechanical nociceptive thresholds regardless of early-life conditions. On the other hand, LBN-reared CIE-2BC males showed reduced open arm exploration in the elevated plus maze and increased immobility in the tail suspension test compared to alcohol-naïve counterparts, while no group differences were detected among control-reared males. Finally, LBN rearing and alcohol exposure did not affect grooming in response to a sucrose spray (splash test), novel object recognition, or corticosterone levels. In summary, the LBN experience accelerates the transition from moderate to excessive alcohol drinking and produces additional indices of affective dysfunction during alcohol withdrawal in C57BL/6J male mice.

•

Early-life adversity was generated by rearing C57BL/6J mouse pups in a limited bedding and nesting (LBN) environment.

•

Alcohol dependence was induced in adulthood via chronic intermittent ethanol (CIE) inhalation.

•

The LBN experience accelerated alcohol intake escalation in males.

•

LBN exacerbated affective disturbances upon CIE withdrawal in males.

•

Alcohol intake in females was insensitive to both LBN and CIE.

Effects of Early-Life Stress on the Brain and Behaviors: Implications of Early Maternal Separation in Rodents

Early-life stress during the prenatal and postnatal periods affects the formation of neural networks that influence brain function throughout life. Previous studies have indicated that maternal separation (MS), a typical rodent model equivalent to early-life stress and, more specifically, to child abuse and/or neglect in humans, can modulate the hypothalamic-pituitary-adrenal (HPA) axis, affecting subsequent neuronal function and emotional behavior. However, the neural basis of the long-lasting effects of early-life stress on brain function has not been clarified. In the present review, we describe the alterations in the HPA-axis activity-focusing on serum corticosterone (CORT)-and in the end products of the HPA axis as well as on the CORT receptor in rodents. We then introduce the brain regions activated during various patterns of MS, including repeated MS and single exposure to MS at various stages before weaning, via an investigation of c-Fos expression, which is a biological marker of neuronal activity. Furthermore, we discuss the alterations in behavior and gene expression in the brains of adult mice exposed to MS. Finally, we ask whether MS repeats itself and whether intergenerational transmission of child abuse and neglect is possible.

Which Zebrafish Strains Are More Suitable to Perform Behavioral Studies? A Comprehensive Comparison by Phenomic Approach

Wild-type (WT) zebrafish are commonly used in behavioral tests, however, the term WT corresponds to many different strains, such as AB, Tübingen long fin (TL), and Wild Indian Karyotype (WIK). Since these strains are widely used, there has to be at least one study to demonstrate the behavioral differences between them. In our study, six zebrafish strains were used, which are AB, absolute, TL, golden, pet store-purchased (PET), and WIK zebrafishes. The behavior of these fishes was tested in a set of behavioral tests, including novel tank, mirror-biting, predator avoidance, social interaction, and shoaling tests. From the results, the differences were observed for all behavioral tests, and each strain displayed particular behavior depending on the tests. In addition, from the heatmap and PCA (principal component analysis) results, two major clusters were displayed, separating the AB and TL zebrafishes with other strains in another cluster. Furthermore, after the coefficient of variation of each strain in every behavioral test was calculated, the AB and TL zebrafishes were found to possess a low percentage of the coefficient of variation, highlighting the strong reproducibility and the robustness of the behaviors tested in both fishes. Each zebrafish strain tested in this experiment showed specifically different behaviors from each other, thus, strain-specific zebrafish behavior should be considered when designing experiments using zebrafish behavior.

Chemogenetic manipulation of the bed nucleus of the stria terminalis counteracts social behavioral deficits induced by early life stress in C57BL/6J mice

Trauma during critical periods of development can induce long-lasting adverse effects. To study neural aberrations resulting from early life stress (ELS), many studies utilize rodent maternal separation, whereby pups are intermittently deprived of maternal care necessary for proper development. This can produce adulthood behavioral deficits related to anxiety, reward, and social behavior. The bed nucleus of the stria terminalis (BNST) encodes aspects of anxiety-like and social behaviors, and also undergoes developmental maturation during the early postnatal period, rendering it vulnerable to effects of ELS. Mice underwent maternal separation (separation 4 hr/day during postnatal day (PD)2-5 and 8 hr/day on PD6-16) with early weaning on PD17, which induced behavioral deficits in adulthood performance on two-part social interaction task designed to test social motivation (choice between a same-sex novel conspecific or an empty cup) and social novelty preference (choice between the original-novel conspecific vs. a new-novel conspecific). We used chemogenetics to non-selectively silence or activate neurons in the BNST to examine its role in social motivation and social novelty preference, in mice with or without the history of ELS. Manipulation of BNST produced differing social behavior effects in non-stressed versus ELS mice; social motivation was decreased in non-stressed mice following BNST activation, but unchanged following BNST silencing, while ELS mice showed no change in social behavior after BNST activation, but exhibited enhancement of social motivation-for which they were deficient prior-following BNST silencing. Findings emphasize the BNST as a potential therapeutic target for social anxiety disorders instigated by childhood trauma.

Time-Dependent Effects of Exposure to Physical and Sexual Violence on Psychopathology Symptoms in Late Childhood: In Search of Sensitive Periods in Development

OBJECTIVE

Exposure to interpersonal violence is a known risk factor for psychopathology. However, it is unclear whether there are sensitive periods when exposure is most deleterious. We aimed to determine whether there were time periods when physical or sexual violence exposure was associated with greater child psychopathology.

METHOD

This study (N = 4,580) was embedded in Generation R, a population-based prospective birth cohort. Timing of violence exposure, reported through maternal reports (child age, 10 years) was categorized by age at first exposure, defined as: very early (0-3 years), early (4-5 years), middle (6-7 years), and late (8+ years) childhood. Using Poisson regression, we assessed the association between timing of first exposure and levels of internalizing and externalizing symptoms, using the Child Behavior Checklist at age 10 years.

RESULTS

Violence exposure at any age was associated with higher internalizing (physical violence: risk ratio [RR] = 1.46, p < 0.0001; sexual violence: RR = 1.30, p < .0001) and externalizing symptoms (physical violence: RR = 1.52, p < 0.0001; sexual violence: RR = 1.31, p = 0.0005). However, the effects of violence were time dependent: compared to children exposed at older ages, children first exposed during very early childhood had greater externalizing symptoms. Sensitivity analyses suggested that these time-based differences emerged slowly across ages 1.5, 3, 6, and 10 years, showing a latency between onset of violence exposure and emergence of symptoms, and were unlikely to be explained by co-occurring adversities.

CONCLUSION

Interpersonal violence is harmful to childhood mental health regardless of when it occurs. However, very early childhood may be a particularly sensitive period when exposure results in worse psychopathology outcomes. Results should be replicated in fully prospective designs.

Neonatal shaking brain injury changes psychological stress-induced neuronal activity in adult male rats

Neonatal shaking brain injury (SBI) leads to increases in anxiety-like behavior and altered hormonal responses to psychological stressors as adults. These abnormalities are hypothesized to be due to a change in sensitization in neuronal circuits as a consequence of neonatal SBI. We examined the effects of neonatal SBI on neuronal activity in the anxiety- and/or stress-related areas of adult rats using Fos immunohistochemistry. Exposure to a novel elevated plus maze (EPM) resulted in a marked increase in Fos expression in the parvocellular (PVNp) and magnocellular parts of the paraventricular nucleus and the ventral part of the bed nucleus of the stria terminalis (vBNST) of shaken rats (S group) compared to non-shaken control rats (C group). On the contrary, Fos expression was significantly lower in the medial nucleus of the amygdala and the ventral subiculum (vS) of S group rats than C group rats exposed to EPM. Although we found no significant correlation in the number of Fos-expressing cells in the vBNST and PVNp in the C group rats, these numbers were significantly correlated in the S group rats. Furthermore, in the S group rats, but not in the C group rats, the number of Fos-expressing cells in the vBNST was inversely correlated with that in the vS. Interestingly, previous neuronal tracing studies have demonstrated direct projections from the vS to the vBNST and from the vBNST to the PVNp. The present data suggest that neonatal SBI can alter neuronal activity in anxiety- and/or stress-related neuronal circuits.

Developmental effects of environmental enrichment on selective and auditory sustained attention

Environmental enrichment (EE) has been used as a positive manipulation in different disease models. However, there is conflicting evidence reported in the literature about the effects of EE. Additionally, the time period that would be most beneficial in implementing environmental enrichment as an intervention is not clear. Our study aimed to systematically compare the prenatal, juvenile, mid-adolescence, and adulthood developmental trajectory to further the understanding of enriched environment's effects on selective and auditory sustained attention, corresponding to behavioral (conceived) and physiological-reflexive (non-conceived) measures. Rats were exposed for 21 days to enriched environment during various developmental periods and compared to age-matched controls. All groups were tested for long-term effects (at postnatal day 120 and onward) on selective and sustained attention. We found that the exposure to enriched environment during mid-adolescence has yielded the most significant and long-term pattern of effects, including selective and auditory sustained attention performance, increased foraging-like behavior and a significant decrease in corticosterone level. Similarly, the exposure to EE at juvenile period improved selective attention, increased foraging-like behavior, and reduced anxiety levels as reflected in the open field as well as in low corticosterone levels. These results specify a crucial period along the developmental trajectory for applying environmental enrichment. Mid-adolescence is suggested, in future basic and translational studies, as the sensitive time period that induces the most beneficial and long-term effects of EE on attention. The current findings suggest that the exposure to EE during mid-adolescence should be further considered and studied as behavioral alternative intervention, or as adjuvant behavioral therapy, aimed to decrease the probability to develop ADHD in post-adolescence period. This suggestion is highly relevant due to the debate regarding the pros and cons of screens usage (e.g. Facebook, online games, etc.) during early life that decreases environmental enrichment, especially, direct social interaction.

Animal models of major depression: drawbacks and challenges

Major depression is a leading contributor to the global burden of disease. This situation is mainly related to the chronicity and/or recurrence of the disorder, and to poor response to antidepressant therapy. Progress in this area requires valid animal models. Current models are based either on manipulating the environment to which rodents are exposed (during the developmental period or adulthood) or biological underpinnings (i.e. gene deletion or overexpression of candidate genes, targeted lesions of brain areas, optogenetic control of specific neuronal populations, etc.). These manipulations can alter specific behavioural and biological outcomes that can be related to different symptomatic and pathophysiological dimensions of major depression. However, animal models of major depression display substantial shortcomings that contribute to the lack of innovative pharmacological approaches in recent decades and which hamper our capabilities to investigate treatment-resistant depression. Here, we discuss the validity of these models, review putative models of treatment-resistant depression, major depression subtypes and recurrent depression. Furthermore, we identify future challenges regarding new paradigms such as those proposing dimensional rather than categorical approaches to depression.

Sexually dimorphic behavioral effects of maternal separation in anorexic rats

Exposure to negative events during the neonatal period is one of the leading factors contributing to the development of psychiatric disorders, including anorexia nervosa. In this study, we investigated the effects of maternal separation (MS) on the development of anorexia in rodents using the mild-stress form of the activity-based anorexia (ABA) model (2 hr of free access to a running wheel and a 1-hr feeding test) in both male and female rats. We assessed anxiety-like and locomotor behavior and hyperactivity with the open field and elevated plus maze tests. Our results showed that ABA rats of both sexes displayed hyperactive behavior associated with reduced anxiety-like behavior when compared to controls. However, a sexually dimorphic effect of MS emerged in anorexic rats: while the females exposed to MS + ABA were hyperactive with diminished anxiety-related behaviors compared to females of the ABA group, MS in males attenuated or did not alter the effects of the ABA protocol. In conclusion, our data reveal that the synergistic effects of MS and ABA on physical activity and anxiety-like behavior act in opposite directions in the two sexes.

How Early Life Stress Impact Maternal Care: A Systematic Review of Rodent Studies

Background: Maternal care refers to the behavior performed by the dam to nourish and protect her litter during its early development. Frequent and high-quality performance of such maternal behaviors is critical for the neurodevelopment of the pups. Maternal exposure to stress during early development can impair maternal care and amplify the deleterious effects of poor maternal caregiving and neglect. As such, a thorough understanding of the effects caused by several models of early life stress on maternal care may yield more insights into the relationship between stress and maternal behavior.

Methods: A systematic review was performed to identify and address the effects of early life stress on maternal behavior. The search was conducted using three online databases: PUBMED, Embase, and Web of Science. To provide clear evidence of the impact of stress on maternal care, in every study, the stress group was always compared to a control group. Outcomes were categorized into eight different behaviors: (1) licking/grooming; (2) arched-back nursing; (3) blanket-nursing/passive nursing; (4) nest building; (5) contact with pups; (6) harmful/adverse caregiving; (7) no contact; (8) nest exits. Additionally, the methodological quality of the studies was evaluated.

Results: A total of 12 different early life stress protocols were identified from the 56 studies included in this systematic review. Our data demonstrate that different stress models can promote specific maternal patterns of behavior. Regarding the maternal separation protocol, we observed an overall increase in nursing and licking/grooming behaviors, which are essential for pup development. An increase in the number of nest exits, which represents a fragmentation of maternal care, was observed in the limited bedding protocol, but the total amount of maternal care appears to remain similar between groups.

Conclusions: Each stress protocol has unique characteristics that increase the difficulty of rendering comparisons of maternal behavior. The increase in maternal care observed in the maternal separation protocol may be an attempt to overcompensate for the time off-nest. Fragmented maternal care is a key component of the limited bedding protocol. Moreover, the methodological approaches to evaluate maternal behavior, such as time, duration, and behavior type should be more homogeneous across studies.

Comorbidities of early-onset temporal epilepsy: Cognitive, social, emotional, and morphologic dimensions

Epilepsy, the most common neurologic disorder in childhood, is associated with a subset of psychiatric dysfunctions, including cognitive deficits, and alterations in emotionality (e.g., anxiety and depression) and social functioning. In the present study, we evaluated an integrative set of behavioral responses, including cognitive/socio-cognitive and emotional dimensions, using a number of behavioral paradigms in the LiCl/pilocarpine model of status epilepticus (SE) in rats. The aims of the study were to examine whether SE affects: 1) non-associative learning (habituation of exploratory behavior); 2) investigatory response to an indifferent stimulus object; 3) sociability/social novelty preference; 4) social recognition or discrimination; and 4) short- and long-term memory in the Morris water maze (MWM). Finally, we investigated the morphology of key brain structures involved in the examined behavioral dysfunctions. SE did not affect habituation to an open-field arena in juvenile (P25), adolescent (P32), or adult (P80) rats. SE rats spent less time in the central part of the arena. SE adolescent rats (P32) displayed a higher number of rearings with a shorter duration. SE rats displayed a markedly attenuated investigatory response to an indifferent stimulus object. SE rats in all age groups demonstrated pronounced deficits in sociability and the preference for social novelty. In addition, SE rats spent a reduced amount of time investigating a juvenile rat upon first exposure. After 30 min re-exposure together with an additional, novel juvenile, the SE rats spent equal time investigating both juveniles. In the MWM task, acquisition was unimpaired but there was a deficit in delayed memory retention after 10 days. SE did not affect cognitive flexibility expressed by reversal learning. Together, these findings suggest that early-life SE leads to alterations in emotional/anxiety-related behavior and affects sociability/preference for social novelty and social discrimination. Early-life SE did not alter acquisition of spatial learning, but it impaired delayed retention. Using Fluoro Jade B staining performed 24 h after SE revealed apparent neurodegeneration in the dorsal hippocampus, mediodorsal thalamic nucleus and medial amygdala, brain areas that are critically involved in network underlying emotional behavior and cognitive functions.

Prenatal stress and elevated seizure susceptibility: Molecular inheritable changes

Stressful episodes are common during early-life and may have a wide range of negative effects on both physical and mental status of the offspring. In addition to various neurobehavioral complications induced by prenatal stress (PS), seizure is a common complication with no fully explained cause. In this study, the association between PS and seizure susceptibility was reviewed focusing on sex differences and various underlying mechanisms. The role of drugs in the initiation of seizure and the effects of PS on the nervous system that prone the brain for seizure, especially the hypothalamic-pituitary-adrenal (HPA) axis, are also discussed in detail by reviewing the papers studying the effect of PS on glutamatergic, gamma-aminobutyric acid (GABA)ergic, and adrenergic systems in the context of seizure and epilepsy. Finally, epigenetic changes in epilepsy are described, and the underlying mechanisms of this change are expanded. As the effects of PS may be life-lasting, it is possible to prevent future psychiatric and behavioral disorders including epilepsy by preventing avoidable PS risk factors.

Inter-individual Variability for High Fat Diet Consumption in Inbred C57BL/6 Mice

Since inbred C57BL/6 mice are known to show inter-individual phenotypic variability for some traits, we tested the hypothesis that inbred C57BL/6 mice display a different tendency to consume a high fat (HF) diet. For this purpose, we used a compilation of HF intake data from an experimental protocol in which satiated mice were exposed to a HF pellet every morning for 2-h over 4 consecutive days. We found that mice displayed a large degree of variability in HF intake. Since day 1 HF intake significantly correlated with HF intake in successive days, we applied a hierarchical clustering algorithm on HF intake measurements in days 2, 3, and 4 in order to classify mice into “low” or “high” HF intake groups. “Low” HF intake group showed a day 1 HF intake similar to that seen in mice exposed to regular chow, while “high” HF intake group showed a higher day 1 HF intake as compared to “low” HF intake group. Both groups of mice increased HF consumption over the successive days, but “high” HF intake group always displayed a higher HF consumption than the “low” HF intake group. As compared to “low” HF intake group, “high” HF intake group showed a higher number of dopamine neurons positive for c-Fos in the VTA after the last event of HF intake. Thus, inbred C57BL/6 mice show inter-individual variability for HF intake and such feature may be linked to a different response to the rewarding properties of the HF diet.

Violence exposure in an urban city: A GxE interaction with aggressive and impulsive behaviors

BACKGROUND

Previous research has demonstrated a reciprocal relationship between community violence exposure and disruptive behavior problems among youth. No study to date, however, has explored the potential interaction between violence exposure in early adolescence and genetics.

METHODS

We explore the gene x environment interaction's impact on teacher-rated aggressive and impulsive behaviors. Violence exposure during the middle school years was assessed using self-report. Genetic data collection occurred in emerging adulthood. A polygenic score was created using findings from a conduct disorder symptomatology genome-wide association study.

RESULTS

Three longitudinal classes of teacher reported aggressive and impulsive behavior were identified. We found a significant relationship between violence exposure and class membership. There was a significant GxE interaction, such that those with below average levels of the polygenic score and who were exposed to violence were more likely to be in the moderately high aggressive and impulsive class as compared to the no to low class.

CONCLUSIONS

These findings highlight the influence of genetic risk together with violence exposure on adolescent problem behavior. Although youth may have little control over the environments in which they live, interventions can and should focus on helping all youth.

Targeted sensory enrichment interventions protect against behavioral and neuroendocrine consequences of early life stress

Both basic and clinical research support the use of tactile stimulation to rescue several neurobiobehavioral consequences that follow early life stress. Here, using a translational rodent model of the neonatal intensive care unit (NICU), we tested the individual prophylactic potential of a variety of sensory interventions including tactile (brushing pups with a paint brush to mimic maternal licking), auditory (a simulated lactating rat dam heart beat), and olfactory (a series of aroma therapy scents) stimulation. The NICU model was developed to mimic not only the reduced parental contact that sick infants receive (by isolating rat pups from their litters), but also the nosocomial infections and medical manipulations associated with this experience (by utilizing a dual lipopolysaccharide injection schedule). Each of the neurobiobehavioral consequences observed were dissociable between isolation and inflammation, or required a combined presentation ('two hits') of the neonatal stressors. Sprague-Dawley rats exposed to these early life stressors presented with sex-specific disruptions in both separation-induced ultrasonic vocalization (USV) distress calls (males & females) and juvenile social play USVs (males only). All three sensory enhancement interventions were associated with the rescue of potentiated distress calls while olfactory stimulation was protective of social vocalizations. Female rats exposed to early life stress experienced precocious puberty and shifts in the hypothalamic GnRh axis; sensory enrichment counter-acted the advanced pubertal onset. Animals that underwent the NICU protocol also displayed maturational acceleration in terms of the loss of the rooting reflex in addition to hyperalgesia, a reduced preference for a novel conspecific, blunted basal plasma corticosterone and reduced hippocampal glucocorticoid receptor expression. These alterations closely simulated the clinical effects of early life adversity in terms of disruptions in the hypothalamic pituitary "stress" axis, social communication and engagement, tactile system processing, and accelerated maturation. Moreover, sensory enrichment attenuated many of these behavioral and neurophysiological alterations, and even slowed maturation. Overall, this supports the translatability of our novel rodent model and its potential utility in understanding how brain maturation and quality of early life experiences may interact to shape the integrity of stress and sensory system development. Future work must determine the appropriate modalities and parameters (e.g. patterning, timing) for effective sensory enrichment interventions.

What life course theoretical models best explain the relationship between exposure to childhood adversity and psychopathology symptoms: recency, accumulation, or sensitive periods?

BACKGROUND

Although childhood adversity is a potent determinant of psychopathology, relatively little is known about how the characteristics of adversity exposure, including its developmental timing or duration, influence subsequent mental health outcomes. This study compared three models from life course theory (recency, accumulation, sensitive period) to determine which one(s) best explained this relationship.

METHODS

Prospective data came from the Avon Longitudinal Study of Parents and Children (n = 7476). Four adversities commonly linked to psychopathology (caregiver physical/emotional abuse; sexual/physical abuse; financial stress; parent legal problems) were measured repeatedly from birth to age 8. Using a statistical modeling approach grounded in least angle regression, we determined the theoretical model(s) explaining the most variability (r2) in psychopathology symptoms measured at age 8 using the Strengths and Difficulties Questionnaire and evaluated the magnitude of each association.

RESULTS

Recency was the best fitting theoretical model for the effect of physical/sexual abuse (girls r2 = 2.35%; boys r2 = 1.68%). Both recency (girls r2 = 1.55%) and accumulation (boys r2 = 1.71%) were the best fitting models for caregiver physical/emotional abuse. Sensitive period models were chosen alone (parent legal problems in boys r2 = 0.29%) and with accumulation (financial stress in girls r2 = 3.08%) more rarely. Substantial effect sizes were observed (standardized mean differences = 0.22-1.18).

CONCLUSIONS

Child psychopathology symptoms are primarily explained by recency and accumulation models. Evidence for sensitive periods did not emerge strongly in these data. These findings underscore the need to measure the characteristics of adversity, which can aid in understanding disease mechanisms and determining how best to reduce the consequences of exposure to adversity.

DNA methylation in adolescents with anxiety disorder: a longitudinal study

Anxiety disorders (AD) typically manifest in children and adolescents and might persist into adulthood. However, there are still few data concerning epigenetic mechanisms associated with onset, persistence or remission of AD over time. We investigated a cohort of adolescents and young adults at baseline (age; 13.19 ± 2.38) and after 5 years and classified them according to the AD diagnosis and their longitudinal trajectories into 4 groups: (1) Typically Developing Comparisons (TDC; control group, n = 14); (2) Incident (AD in the second evaluation only, n = 11); (3) Persistent (AD in both evaluations, n = 14) and (4) Remittent (AD in the first evaluation only, n = 8). DNA methylation was evaluated with the Infinium HumanMethylation450 BeadChip from saliva samples collected at both evaluations. Gene set enrichment analysis was applied to consider biological pathways. We found decreased DNA methylation in TDC group while the chronic cases of AD presented hypermethylation in central nervous system development pathways. Moreover, we showed that this persistent group also presented hypermethylation while the other three groups were associated with hypomethylation in nervous system development pathway. Incidence and remission groups were associated with increased and decreased methylation in neuron development pathways, respectively. Larger studies are likely to detect specific genes relevant to AD.

Anxiety-like behavior and other consequences of early life stress in mice with increased protein kinase A activity

Anxiety disorders are associated with abnormalities in fear-learning and bias to threat; early life experiences are influential to the development of an anxiety-like phenotype in adulthood. We recently reported that adult mice (Prkar1a+/-) with haploinsufficiency for the main regulatory subunit of the protein kinase A (PKA) exhibit an anxiety-like phenotype associated with increased PKA activity in the amygdala. PKA is the main effector of cyclic adenosine mono-phosphate signaling, a key pathway involved in the regulation of fear learning. Since anxiety has developmental and genetic components, we sought to examine the interaction of a genetic defect associated with anxiety phenotype and early life experiences. We investigated the effects of neonatal maternal separation or tactile stimulation on measures of behavior typical to adolescence as well as developmental changes in the behavioral phenotype between adolescent and adult wild-type (WT) and Prkar1a+/- mice. Our results showed developmental differences in assays of anxiety and novelty behavior for both genotypes. Adolescent mice showed increased exploratory and novelty seeking behavior compared to adult counterparts. However, early life experiences modulated behavior in adolescent WT differently than in adolescent Prkar1a+/- mice. Adolescent WT mice exposed to early life tactile stimulation showed attenuation of anxiety-like behavior, whereas an increase in exploratory behavior was found in Prkar1a+/- adolescent mice. The finding of behavioral differences that are apparent during adolescence in Prkar1a^+/- mice suggests that long-term exposure of the brain to increased PKA activity during critical developmental periods contributes to the anxiety-like phenotype noted in the adult animals with increased PKA activity.

Combined early life stressors: Prenatal nicotine and maternal deprivation interact to influence affective and drug seeking behavioral phenotypes in rats

Early life stress (ELS) increases the risk for later cognitive and emotional dysfunction, and has been implicated in the etiology of multiple psychiatric disorders. We hypothesize that combined insults during gestation and infancy, critical periods of neural development, could exacerbate neuropsychiatric outcomes in later life. Thus, we investigated the effects of maternal deprivation (MD) stress alone or combined with prenatal nicotine exposure (PNE) on negative affective states, ethanol drinking, and development of mesolimbic loci that regulate depression and drug dependence. On the elevated plus maze (EPM), MD rats exhibited ∼50% increase in risk-taking behavior/decreased anxiety when compared to control, but the combined MD + PNE did not affect this specific behavior. In the open field test, however, both MD and MD + PNE groups showed 2-fold greater locomotor activity. Furthermore, whereas MD showed greater latency to fall at 40 RPM on the rotarod compared to control, the MD + PNE animals' latency to fall was significantly greater at all RPMs tested, with an approximate 15% enhancement in motor coordination overall compared to control and MD. Analyses of depressive symptomatology with the forced swim test (FST) yielded 2- and 3-fold higher immobility times in MD and MD + PNE respectively. When tested in an operant drinking paradigm to quantify the effect of treatment on 10%v/v ethanol drinking, the MD and MD + PNE groups showed heightened ethanol consumption by ∼3- and 2-fold respectively. However, the experience of PNE reduced ethanol consumption in adults relative to MD alone. To test the stressors' impact on neurons in the amygdala and ventral tegmental area (VTA), mesolimbic anatomical regions associated with mood and reward, unbiased stereological measurements were performed and revealed ∼15% increase in number and density of neurons in the amygdala for both MD and MD + PNE, and ∼13% reduction in dopaminergic-like neurons in the VTA compared to control. We report here that multiple early stressors including prenatal nicotine and MD can modulate the neuroanatomy of the amygdala and VTA. These early life stressors can interact to influence the development of depressive-like and addictive behaviors.

Neonatal whisker trimming in WAG/Rij rat pups causes developmental delay, encourages maternal care and affects exploratory activity in adulthood

WAG/Rij rats are genetically predisposed to absence epilepsy. Maternal behavior in WAG/Rij female rats is known to differ from that in non-epileptic females. We hypothesize that (1) mother's behavior may be changed as response to changes in pup's conditions; (2) sensory deprivation at the neonatal age affect learning and behavior in adulthood. All whiskers in WAG/Rij rat pups were trimmed daily during PN1-PN8. Maternal behavior was examined during the same period. It was found that in the control group, WAG/Rij females often demonstrated abnormally long (>1 min) repetitive purposeless stereotypical actions that were roughly classified as compulsive-like behavior. Mothers of the trimmed pups showed less compulsive-like behavior and more intensively interacted with pups and built better nests. Rat pups in the trimmed group had lower body weight on PN7-PN19 as compared to the control. In the trimmed group, maturation of motor skills and early behavioral patterns (i.e. walking, grooming, vertical activity, motor functions of forelimbs) showed 1-2 days delay in comparison to the control. At the age of 2-2.5 months, the locomotor activity in the trimmed rats differed from the control, but the level of anxiety was the same (the open field and the elevated plus maze). At the age of 6 months, the trimmed and control rats showed no differences in conditioned avoidance learning test, therefore, neonatal whisker trimming did not influence fear-based learning abilities in adulthood. It is hypothesized that an enhanced maternal care is capable to modulate development of brain functions in sensory deprived progeny.

Early Life Stress, Depression And Parkinson's Disease: A New Approach

This review aims to shed light on the relationship that involves exposure to early life stress, depression and Parkinson's disease (PD). A systematic literature search was conducted in Pubmed, MEDLINE, EBSCOHost and Google Scholar and relevant data were submitted to a meta-analysis . Early life stress may contribute to the development of depression and patients with depression are at risk of developing PD later in life. Depression is a common non-motor symptom preceding motor symptoms in PD. Stimulation of regions contiguous to the substantia nigra as well as dopamine (DA) agonists have been shown to be able to attenuate depression. Therefore, since PD causes depletion of dopaminergic neurons in the substantia nigra, depression, rather than being just a simple mood disorder, may be part of the pathophysiological process that leads to PD. It is plausible that the mesocortical and mesolimbic dopaminergic pathways that mediate mood, emotion, and/or cognitive function may also play a key role in depression associated with PD. Here, we propose that a medication designed to address a deficiency in serotonin is more likely to influence motor symptoms of PD associated with depression. This review highlights the effects of an antidepressant, Fluvoxamine maleate, in an animal model that combines depressive-like symptoms and Parkinsonism.