Stressed-out, or in (utero)?

Enduring memory consequences of early-life stress / adversity: Structural, synaptic, molecular and epigenetic mechanisms

Adverse early life experiences are strongly associated with reduced cognitive function throughout life. The link is strong in many human studies, but these do not enable assigning causality, and the limited access to the live human brain can impede establishing the mechanisms by which early-life adversity (ELA) may induce cognitive problems. In experimental models, artificially imposed chronic ELA/stress results in deficits in hippocampus dependent memory as well as increased vulnerability to the deleterious effects of adult stress on memory. This causal relation of ELA and life-long memory impairments provides a framework to probe the mechanisms by which ELA may lead to human cognitive problems. Here we focus on the consequences of a one-week exposure to adversity during early postnatal life in the rodent, the spectrum of the ensuing memory deficits, and the mechanisms responsible. We highlight molecular, cellular and circuit mechanisms using convergent trans-disciplinary approaches aiming to enable translation of the discoveries in experimental models to the clinic.

Serum matrix metallopeptidase-9 levels in infantile epileptic spasms syndrome of unknown etiology

PURPOSE

Epileptic spasms are the primary symptom of infantile epileptic spasms syndrome (IESS); however, their direct impact on blood-brain barrier (BBB) function is unknown. Matrix metallopeptidase-9 (MMP-9), degrades type IV collagen, a key component of the blood-brain barrier, while tissue inhibitor of metalloproteinase-1 (TIMP-1) suppresses its activity, protecting BBB integrity. This study aimed to assess serum MMP-9 and TIMP-1 levels in patients with IESS of unknown etiology.

METHODS

We prospectively assessed serum MMP-9 and TIMP-1 levels prior to administering vigabatrin or adrenocorticotropic hormone therapy in patients with IESS of unknown etiology at Saitama Children's Medical Center between February 2012 and December 2023. We compared these biomarkers between patients with epileptic spasms and age-matched controls and performed a curve regression analysis between the biomarkers and the frequency of epileptic spasms. Additionally, we assessed whether MMP-9 and TIMP-1 levels were diagnostic predictors of IESS.

RESULTS

This study included 22 patients with IESS (11 males) and 12 controls. Serum MMP-9 and MMP-9/TIMP-1 ratios were higher in patients with IESS than in controls (p < 0.001 and p = 0.002, respectively). A high frequency of epileptic spasms also led to higher serum MMP-9 levels (y = 0.0871x2 + 0.195x + 195.15, R² = 0.77, p < 0.001). Using MMP >188 ng/mL as the cutoff level, the sensitivity for diagnosing IESS was 95.5 %, the specificity was 75.0 %, the positive likelihood ratio was 3.82 (95 % confidence interval (CI) 1.43-10.22), and the relative risk was 8.75 (95 % CI 1.36-56.5).

CONCLUSION

Patients with IESS had elevated serum MMP-9 levels, suggesting an association between epileptic spasms and blood-brain barrier dysfunction. MMP-9 level measurement may be useful for diagnosing suspected patients.

Cord serum cytokines at birth and children's trajectories of mood dysregulation symptoms from 3 to 8 years: The EDEN birth cohort

There is growing evidence that in utero imbalance immune activity plays a role in the development of neurodevelopmental and psychiatric disorders in children. Mood dysregulation (MD) is a debilitating transnosographic syndrome whose underlying pathophysiological mechanisms could be revealed by studying its biomarkers using the Research Domain Criteria (RDoC) model. Our aim was to study the association between the network of cord serum cytokines, and mood dysregulation trajectories in offsprings between 3 and 8 years of age. We used the data of a study nested in the French birth cohort EDEN that took place from 2003 to 2014 and followed mother-child dyads from the second trimester of pregnancy until the children were 8 years of age. The 2002 mother-child dyads were recruited from the general population through their pregnancy follow-up in two French university hospitals. 871 of them were included in the nested cohort and cord serum cytokine levels were measured at birth. Children's mood dysregulation symptoms were assessed with the Strengths and Difficulties Questionnaire Dysregulation Profile at the ages 3, 5 and 8 years in order to model their mood dysregulation trajectories. Out of the 871 participating dyads, 53% of the children were male. 2.1% of the children presented a high mood dysregulation trajectory whereas the others were considered as physiological variations. We found a significant negative association between TNF-α cord serum levels and a high mood dysregulation trajectory when considering confounding factors such as maternal depression during pregnancy (adjusted Odds Ratio (aOR) = 0.35, 95% Confidence Interval (CI) [0.18-0.67]). Immune imbalance at birth could play a role in the onset of mood dysregulation symptoms. Our findings throw new light on putative immune mechanisms implicated in the development of mood dysregulation and should lead to future animal and epidemiological studies.

3R-Refinement principles: elevating rodent well-being and research quality

This review article delves into the details of the 3R-Refinement principles as a vital framework for ethically sound rodent research laboratory. It highlights the core objective of the refinement protocol, namely, to enhance the well-being of laboratory animals while simultaneously improving the scientific validity of research outcomes. Through an exploration of key components of the refinement principles, the article outlines how these ethics should be implemented at various stages of animal experiments. It emphasizes the significance of enriched housing environments that reduce stress and encourage natural behaviors, non-restraint methods in handling and training, refined dosing and sampling techniques that prioritize animal comfort, the critical role of optimal pain management and the importance of regular animal welfare assessment in maintaining the rodents well-being. Additionally, the advantages of collaboration with animal care and ethics committees are also mentioned. The other half of the article explains the extensive benefits of the 3R-Refinement protocol such as heightened animal welfare, enhanced research quality, reduced variability, and positive feedback from researchers and animal care staff. Furthermore, it addresses avenues for promoting the adoption of the protocol, such as disseminating best practices, conducting training programs, and engaging with regulatory bodies. Overall, this article highlights the significance of 3R-Refinement protocol in aligning scientific advancement with ethical considerations along with shaping a more compassionate and responsible future for animal research.

Increases in maternal depressive symptoms during pregnancy and infant cortisol reactivity: Mediation by placental corticotropin-releasing hormone

BACKGROUND

Maternal depressive symptoms in pregnancy may affect offspring health through prenatal programming of the hypothalamic-pituitary-adrenal (HPA) axis. The biological mechanisms that explain the associations between maternal prenatal depressive symptoms and offspring HPA axis regulation are not yet clear. This pre-registered investigation examines whether patterns of maternal depressive symptoms in pregnancy are associated with infant cortisol reactivity and whether this association is mediated by changes in placental corticotropin-releasing hormone (pCRH).

METHOD

A sample of 174 pregnant women completed assessments in early, mid, and late pregnancy that included standardized measures of depressive symptoms and blood samples for pCRH. Infant cortisol reactivity was assessed at 1 and 6 months of age.

RESULTS

Greater increases in maternal depressive symptoms in pregnancy were associated with higher cortisol infant cortisol reactivity at 1 and 6 months. Greater increases in maternal depressive symptoms in pregnancy were associated with greater increases in pCRH from early to late pregnancy which in turn were associated with higher infant cortisol reactivity.

CONCLUSIONS

Increases in maternal depressive symptoms and pCRH over pregnancy may contribute to higher infant cortisol reactivity. These findings help to elucidate the prenatal biopsychosocial processes contributing to offspring HPA axis regulation early in development.

Neurocognitive effects of stress: a metaparadigm perspective

Stressful experiences, both physical and psychological, that are overwhelming (i.e., inescapable and unpredictable), can measurably affect subsequent neuronal properties and cognitive functioning of the hippocampus. At the cellular level, stress has been shown to alter hippocampal synaptic plasticity, spike and local field potential activity, dendritic morphology, neurogenesis, and neurodegeneration. At the behavioral level, stress has been found to impair learning and memory for declarative (or explicit) tasks that are based on cognition, such as verbal recall memory in humans and spatial memory in rodents, while facilitating those that are based on emotion, such as differential fear conditioning in humans and contextual fear conditioning in rodents. These vertically related alterations in the hippocampus, procedurally observed after subjects have undergone stress, are generally believed to be mediated by recurrently elevated circulating hypothalamic-pituitary-adrenal (HPA) axis effector hormones, glucocorticoids, directly acting on hippocampal neurons densely populated with corticosteroid receptors. The main purposes of this review are to (i) provide a synopsis of the neurocognitive effects of stress in a historical context that led to the contemporary HPA axis dogma of basic and translational stress research, (ii) critically reappraise the necessity and sufficiency of the glucocorticoid hypothesis of stress, and (iii) suggest an alternative metaparadigm approach to monitor and manipulate the progression of stress effects at the neural coding level. Real-time analyses can reveal neural activity markers of stress in the hippocampus that can be used to extrapolate neurocognitive effects across a range of stress paradigms (i.e., resolve scaling and dichotomous memory effects issues) and understand individual differences, thereby providing a novel neurophysiological scaffold for advancing future stress research.

A framework for testing pathways from prenatal stress-responsive hormones to cardiovascular disease risk

Cardiovascular disease (CVD) is a leading cause of death globally, with the prevalence projected to keep rising. Risk factors for adult CVD emerge at least as early as the prenatal period. Alterations in stress-responsive hormones in the prenatal period are hypothesized to contribute to CVD in adulthood, but little is known about relations between prenatal stress-responsive hormones and early precursors of CVD, such as cardiometabolic risk and health behaviors. The current review presents a theoretical model of the relation between prenatal stress-responsive hormones and adult CVD through cardiometabolic risk markers (e.g., rapid catch-up growth, high BMI/adiposity, high blood pressure, and altered blood glucose, lipids, and metabolic hormones) and health behaviors (e.g., substance use, poor sleep, poor diet and eating behaviors, and low physical activity levels). Emerging evidence in human and non-human animal literatures suggest that altered stress-responsive hormones during gestation predict higher cardiometabolic risk and poorer health behaviors in offspring. This review additionally highlights limitations of the current literature (e.g., lack of racial/ethnic diversity, lack of examination of sex differences), and discusses future directions for this promising area of research.

Maturation of large-scale brain systems over the first month of life

The period immediately after birth is a critical developmental window, capturing rapid maturation of brain structure and a child's earliest experiences. Large-scale brain systems are present at delivery, but how these brain systems mature during this narrow window (i.e. first weeks of life) marked by heightened neuroplasticity remains uncharted. Using multivariate pattern classification techniques and functional connectivity magnetic resonance imaging, we detected robust differences in brain systems related to age in newborns (n = 262; R2 = 0.51). Development over the first month of life occurred brain-wide, but differed and was more pronounced in brain systems previously characterized as developing early (i.e. sensorimotor networks) than in those characterized as developing late (i.e. association networks). The cingulo-opercular network was the only exception to this organizing principle, illuminating its early role in brain development. This study represents a step towards a normative brain "growth curve" that could be used to identify atypical brain maturation in infancy.

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'.

Maternal separation and TNBS-induced gut inflammation synergistically alter the sexually differentiated stress response in rats

BACKGROUND

Neonatal maternal separation (MS) has been used to model long-lasting changes in behavior caused by neuroplastic changes associated with exposure to early-life stress. Earlier studies showed that transient gut inflammation can influence the development of irritable bowel syndrome (IBS). A prevailing paradigm of the etiology of IBS is that transient noxious events lead to long-lasting sensitization of the neural pain circuit, despite complete resolution of the initiating event. This study characterizes the changes in behaviors and neuroendocrine parameters after MS and early-phase trinitrobenzene sulfonic acid (TNBS)-induced colitis. We tested the hypothesis that MS and gut inflammation synergistically induce (1) hyperactivity in male rats and anxiety-like behaviors in female rats and (2) activation of the HPA axis in female rats and deactivation of the HPA axis in male rats after colorectal distention (CRD).

METHODS

Male and female rat pups were separated from their dams for 180 min daily from postnatal day (PND) 2 to PND 14 (MS). Early-phase colitis was induced by colorectal administration with TNBS on PND 8. The elevated plus-maze test was performed at 7 weeks. Tonic CRD was performed at 60 mmHg for 15 min at 8 weeks. Plasma ACTH and serum corticosterone were measured at baseline or after the CRD. Analysis of variance was performed for comparison among controls, TNBS, MS, and MS + TNBS.

RESULTS

In male rats, the time spent in open arms significantly differed among the groups (p < 0.005). The time spent in open arms in male MS + TNBS rats was significantly higher than that of controls (p < 0.009) or TNBS rats (p < 0.031, post hoc test). Female rats showed no difference in the time spent in open arms among the groups. MS and gut inflammation induced an increase in plasma ACTH in female rats but not in male rats at baseline.

CONCLUSIONS

These findings suggest that MS and gut inflammation synergistically induce hyperactive behavior or exaggerated hypothalamic-pituitary-adrenal axis function depending on sex.

Points of divergence on a bumpy road: early development of brain and immune threat processing systems following postnatal adversity

Lifelong indices of maladaptive behavior or illness often stem from early physiological aberrations during periods of dynamic development. This is especially true when dysfunction is attributable to early life adversity (ELA), when the environment itself is unsuitable to support development of healthy behavior. Exposure to ELA is strongly associated with atypical sensitivity and responsivity to potential threats-a characteristic that could be adaptive in situations where early adversity prepares individuals for lifelong danger, but which often manifests in difficulties with emotion regulation and social relationships. By synthesizing findings from animal research, this review will consider threat sensitivity through the lenses of associated corticolimbic brain circuitry and immune mechanisms, both of which are immature early in life to maximize adaptation for protection against environmental challenges to an individual's well-being. The forces that drive differential development of corticolimbic circuits include caretaking stimuli, physiological and psychological stressors, and sex, which influences developmental trajectories. These same forces direct developmental processes of the immune system, which bidirectionally communicates with sensory systems and emotion regulation circuits within the brain. Inflammatory signals offer a further force influencing the timing and nature of corticolimbic plasticity, while also regulating sensitivity to future threats from the environment (i.e., injury or pathogens). The early development of these systems programs threat sensitivity through juvenility and adolescence, carving paths for probable function throughout adulthood. To strategize prevention or management of maladaptive threat sensitivity in ELA-exposed populations, it is necessary to fully understand these early points of divergence.

The rearrangement of actin cytoskeleton in mossy fiber synapses in a model of experimental febrile seizures

Background

Experimental complex febrile seizures induce a persistent hippocampal hyperexcitability and an enhanced seizure susceptibility in adulthood. The rearrangement of filamentous actin (F-actin) enhances the excitability of hippocampus and contributes to epileptogenesis in epileptic models. However, the remodeling of F-actin after prolonged febrile seizures is to be determined.

Methods

Prolonged experimental febrile seizures were induced by hyperthermia on P10 and P14 rat pups. Changes of actin cytoskeleton in hippocampal subregions were examined at P60 and the neuronal cells and pre- /postsynaptic components were labeled.

Results

F-actin was increased significantly in the stratum lucidum of CA3 region in both HT + 10D and HT + 14D groups and further comparison between the two groups showed no significant difference. The abundance of ZNT3, the presynaptic marker of mossy fiber (MF)-CA3 synapses, increased significantly whereas the postsynaptic marker PSD95 did not change significantly. Overlapping area of F-actin and ZNT3 showed a significant increase in both HT+ groups. The results of cell counts showed no significant increase or decrease in the number of neurons in each area of hippocampus.

Conclusion

F-actin was significantly up-regulated in the stratum lucidum of CA3, corresponding to the increase of the presynaptic marker of MF-CA3 synapses after prolonged febrile seizures, which may enhance the excitatory output from the dentate gyrus to CA3 and contribute to the hippocampal hyperexcitability.

Long-term serotonin abnormalities in the brain of immature rats subjected to febrile seizures

Objectives

Febrile seizures (FS) are the most common neurological disorder at a young age in humans. Animal models of hyperthermia-induced seizures provide a tool to investigate the underlying mechanisms of FS related to epilepsy development and its co-morbidities. The present study investigates the alterations in monoamine neurotransmitters in two brain areas: the cortex and the hippo-campus in animals subjected to prolonged FS at their immature age.

Materials and Methods

Experimental animals were divided into three groups: cage-control group (NHT-NFS), positive hyperthermic control group (HT-NFS), and the hyperthermia-induced febrile seizure group (HT-FS). Each group was further subdivided into young (Y) and adult (A) groups.

Results

There were significant changes in the cortical and hippocampal serotonin neurotransmitters that were persistent until adulthood. However, the changes in the two other neurotransmitters, norepinephrine and dopamine, were transient and have been recovered in adulthood.

Conclusion

The present study sheds more light on the importance of monoamine neurotransmitters in epileptogenesis following FS.

Longitudinal and prospective assessment of prenatal maternal sleep quality and associations with newborn hippocampal and amygdala volume

BACKGROUND

The rapid maturation of the fetal brain renders the fetus susceptible to prenatal environmental signals. Prenatal maternal sleep quality is known to have important health implications for newborns including risk for preterm birth, however, the effect on the fetal brain is poorly understood.

METHOD

Participants included 94 pregnant participants and their newborns (53% female). Pregnant participants (Mage = 30; SDage= 5.29) reported on sleep quality three times throughout pregnancy. Newborn hippocampal and amygdala volumes were assessed using structural magnetic resonance imaging. Multilevel modeling was used to test the associations between trajectories of prenatal maternal sleep quality and newborn hippocampal and amygdala volume.

RESULTS

The overall trajectory of prenatal maternal sleep quality was associated with hippocampal volume (left: b = 0.00003, p = 0.013; right: b = 0.00003, p = .008). Follow up analyses assessing timing of exposure indicate that poor sleep quality early in pregnancy was associated with larger hippocampal volume bilaterally (e.g., late gestation left: b = 0.002, p = 0.24; right: b = 0.004, p = .11). Prenatal sleep quality was not associated with amygdala volume.

CONCLUSION

These findings highlight the implications of poor prenatal maternal sleep quality and its role in contributing to newborn hippocampal development.

The outcome of early life status epilepticus—lessons from laboratory animals

Status epilepticus (SE) is the most common neurologic emergency in children. Both clinical and laboratory studies have demonstrated that SE in early life can cause brain damage and permanent behavioral abnormalities, trigger epileptogenesis, and interfere with normal brain development. In experimental rodent models, the consequences of seizures are dependent upon age, the model used, and seizure duration. In studies involving neonatal and infantile animals, the model used, experimental design, conditions during the experiment, and manipulation of animals can significantly affect the course of the experiments as well as the results obtained. Standardization of laboratory approaches, harmonization of scientific methodology, and improvement in data collection can improve the comparability of data among laboratories.

Time and age dependent regulation of neuroinflammation in a rat model of mesial temporal lobe epilepsy: Correlation with human data

Acute brain insults trigger diverse cellular and signaling responses and often precipitate epilepsy. The cellular, molecular and signaling events relevant to the emergence of the epileptic brain, however, remain poorly understood. These multiplex structural and functional alterations tend also to be opposing - some homeostatic and reparative while others disruptive; some associated with growth and proliferation while others, with cell death. To differentiate pathological from protective consequences, we compared seizure-induced changes in gene expression hours and days following kainic acid (KA)-induced status epilepticus (SE) in postnatal day (P) 30 and P15 rats by capitalizing on age-dependent differential physiologic responses to KA-SE; only mature rats, not immature rats, have been shown to develop spontaneous recurrent seizures after KA-SE. To correlate gene expression profiles in epileptic rats with epilepsy patients and demonstrate the clinical relevance of our findings, we performed gene analysis on four patient samples obtained from temporal lobectomy and compared to four control brains from NICHD Brain Bank. Pro-inflammatory gene expressions were at higher magnitudes and more sustained in P30. The inflammatory response was driven by the cytokines IL-1β, IL-6, and IL-18 in the acute period up to 72 h and by IL-18 in the subacute period through the 10-day time point. In addition, a panoply of other immune system genes was upregulated, including chemokines, glia markers and adhesion molecules. Genes associated with the mitogen activated protein kinase (MAPK) pathways comprised the largest functional group identified. Through the integration of multiple ontological databases, we analyzed genes belonging to 13 separate pathways linked to Classical MAPK ERK, as well as stress activated protein kinases (SAPKs) p38 and JNK. Interestingly, genes belonging to the Classical MAPK pathways were mostly transiently activated within the first 24 h, while genes in the SAPK pathways had divergent time courses of expression, showing sustained activation only in P30. Genes in P30 also had different regulatory functions than in P15: P30 animals showed marked increases in positive regulators of transcription, of signaling pathways as well as of MAPKKK cascades. Many of the same inflammation-related genes as in epileptic rats were significantly upregulated in human hippocampus, higher than in lateral temporal neocortex. They included glia-associated genes, cytokines, chemokines and adhesion molecules and MAPK pathway genes. Uniquely expressed in human hippocampus were adaptive immune system genes including immune receptors CDs and MHC II HLAs. In the brain, many immune molecules have additional roles in synaptic plasticity and the promotion of neurite outgrowth. We propose that persistent changes in inflammatory gene expression after SE leads not only to structural damage but also to aberrant synaptogenesis that may lead to epileptogenesis. Furthermore, the sustained pattern of inflammatory genes upregulated in the epileptic mature brain was distinct from that of the immature brain that show transient changes and are resistant to cell death and neuropathologic changes. Our data suggest that the epileptogenic process may be a result of failed cellular signaling mechanisms, where insults overwhelm the system beyond a homeostatic threshold.

Intranasal Insulin Attenuates the Long-Term Adverse Effects of Neonatal Hyperglycemia on the Hippocampus in Rats

Hyperglycemia due to relative hypoinsulinism is common in extremely preterm infants and is associated with hippocampus-mediated long-term cognitive impairment. In neonatal rats, hypoinsulinemic hyperglycemia leads to oxidative stress, altered neurochemistry, microgliosis, and abnormal synaptogenesis in the hippocampus. Intranasal insulin (INS) bypasses the blood-brain barrier, targets the brain, and improves synaptogenesis in rodent models, and memory in adult humans with Alzheimer's disease or type 2 diabetes, without altering the blood levels of insulin or glucose. To test whether INS improves hippocampal development in neonatal hyperglycemia, rat pups were subjected to hypoinsulinemic hyperglycemia by injecting streptozotocin (STZ) at a dose of 80 mg/kg i.p. on postnatal day (P) 2 and randomized to INS, 0.3U twice daily from P3-P6 (STZ + INS group), or no treatment (STZ group). The acute effects on hippocampal neurochemical profile and transcript mRNA expression of insulin receptor (Insr), glucose transporters (Glut1, Glut4, and Glut8), and poly(ADP-ribose) polymerase-1 (Parp1, a marker of oxidative stress) were determined on P7 using in vivo 1H MR spectroscopy (MRS) and qPCR. The long-term effects on the neurochemical profile, microgliosis, and synaptogenesis were determined at adulthood using 1H MRS and histochemical analysis. Relative to the control (CONT) group, mean blood glucose concentration was higher from P3 to P6 in the STZ and STZ + INS groups. On P7, MRS showed 10% higher taurine concentration in both STZ groups. qPCR showed 3-folds higher Insr and 5-folds higher Glut8 expression in the two STZ groups. Parp1 expression was 18% higher in the STZ group and normal in the STZ + INS group. At adulthood, blood glucose concentration in the fed state was higher in the STZ and STZ + INS groups. MRS showed 59% higher brain glucose concentration and histochemistry showed microgliosis in the hippocampal subareas in the STZ group. Brain glucose was normal in the STZ + INS group. Compared with the STZ group, phosphocreatine and phosphocreatine/creatine ratio were higher, and microglia in the hippocampal subareas fewer in the STZ + INS group (p < 0.05 for all). Neonatal hyperglycemia was associated with abnormal glucose metabolism and microgliosis in the adult hippocampus. INS administration during hyperglycemia attenuated these adverse effects and improved energy metabolism in the hippocampus.

Neurodevelopmental origins of substance use disorders: Evidence from animal models of early-life adversity and addiction

Addiction is a chronic relapsing disorder with devastating personal, societal, and economic consequences. In humans, early-life adversity (ELA) such as trauma, neglect, and resource scarcity are linked with increased risk of later-life addiction, but the brain mechanisms underlying this link are still poorly understood. Here, we focus on data from rodent models of ELA and addiction, in which causal effects of ELA on later-life responses to drugs and the neurodevelopmental mechanisms by which ELA increases vulnerability to addiction can be determined. We first summarize evidence for a link between ELA and addiction in humans, then describe how ELA is commonly modeled in rodents. Since addiction is a heterogeneous disease with many individually varying behavioral aspects that may be impacted by ELA, we next discuss common rodent assays of addiction-like behaviors. We then summarize the specific addiction-relevant behavioral phenotypes caused by ELA in male and female rodents and discuss some of the underlying changes in brain reward and stress circuits that are likely responsible. By better understanding the behavioral and neural mechanisms by which ELA promotes addiction vulnerability, we hope to facilitate development of new approaches for preventing or treating addiction in those with a history of ELA.

High, in Contrast to Low Levels of Acute Stress Induce Depressive-like Behavior by Involving Astrocytic, in Addition to Microglial P2X7 Receptors in the Rodent Hippocampus

Extracellular adenosine 5'-triphosphate (ATP) in the brain is suggested to be an etiological factor of major depressive disorder (MDD). It has been assumed that stress-released ATP stimulates P2X7 receptors (Rs) at the microglia, thereby causing neuroinflammation; however, other central nervous system (CNS) cell types such as astrocytes also possess P2X7Rs. In order to elucidate the possible involvement of the MDD-relevant hippocampal astrocytes in the development of a depressive-like state, we used various behavioral tests (tail suspension test [TST], forced swim test [FST], restraint stress, inescapable foot shock, unpredictable chronic mild stress [UCMS]), as well as fluorescence immunohistochemistry, and patch-clamp electrophysiology in wild-type (WT) and genetically manipulated rodents. The TST and FST resulted in learned helplessness manifested as a prolongation of the immobility time, while inescapable foot shock caused lower sucrose consumption as a sign of anhedonia. We confirmed the participation of P2X7Rs in the development of the depressive-like behaviors in all forms of acute (TST, FST, foot shock) and chronic stress (UCMS) in the rodent models used. Further, pharmacological agonists and antagonists acted in a different manner in rats and mice due to their diverse potencies at the respective receptor orthologs. In hippocampal slices of mice and rats, only foot shock increased the current responses to locally applied dibenzoyl-ATP (Bz-ATP) in CA1 astrocytes; in contrast, TST and restraint depressed these responses. Following stressful stimuli, immunohistochemistry demonstrated an increased co-localization of P2X7Rs with a microglial marker, but no change in co-localization with an astroglial marker. Pharmacological damage to the microglia and astroglia has proven the significance of the microglia for mediating all types of depression-like behavioral reactions, while the astroglia participated only in reactions induced by strong stressors, such as foot shock. Because, in addition to acute stressors, their chronic counterparts induce a depressive-like state in rodents via P2X7R activation, we suggest that our data may have relevance for the etiology of MDD in humans.

Serum matrix metallopeptidase-9 and tissue inhibitor of metalloproteinase-1 levels may predict response to adrenocorticotropic hormone therapy in patients with infantile spasms

OBJECTIVE

To evaluate whether serum matrix metallopeptidase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) levels predict response to adrenocorticotropic hormone (ACTH) therapy in patients with infantile spasms.

METHODS

We prospectively evaluated patients with infantile spasms who were referred to Saitama Children's Medical Center from January 2011 to December 2020. We measured Q-albumin and serum MMP-9 and TIMP-1 levels before ACTH therapy. Patients were divided into three groups based on the etiology of their infantile spasms: those with an unknown etiology and normal development (unknown-normal group); those with a structural and acquired etiology (structural-acquired group); and those with a structural and congenital, genetic, metabolic, or unknown etiology with developmental delay (combined-congenital group). Responders were defined as those having complete cessation of spasms for more than 3 months with the resolution of hypsarrhythmia on electroencephalography during ACTH therapy.

RESULTS

We collected serum from 36 patients with West syndrome and five patients with infantile spasms without hypsarrhythmia before ACTH therapy. Twenty-three of 41 patients (56.1%) were responders, including 8/8 (100%) in the unknown-normal group, 6/9 (66.7%) in the structural-acquired group, and 9/24 (37.5%) in the combined-congenital group. The serum MMP-9 level and MMP-9/TIMP-1 ratio were significantly higher in responders than in nonresponders (P = 0.001 for both).

CONCLUSION

A therapeutic response to ACTH was associated with a higher serum MMP-9 level and higher MMP-9/TIMP-1 ratio in patients with infantile spasms. Therefore, these biomarkers may predict responses to ACTH therapy in this patient population.

Inhibition of adult neurogenesis reduces avoidance behavior in male, but not female, mice subjected to early life adversity

Early life adversity (ELA) increases the risk of developing neuropsychiatric illnesses such as anxiety disorders. However, the mechanisms connecting these negative early life experiences to illness later in life remain unclear. In rodents, plasticity mechanisms, specifically adult neurogenesis in the ventral hippocampus, have been shown to be altered by ELA and important for buffering against detrimental stress-induced outcomes. The current study sought to explore whether adult neurogenesis contributes to ELA-induced changes in avoidance behavior. Using the GFAP-TK transgenic model, which allows for the inhibition of adult neurogenesis, and CD1 littermate controls, we subjected mice to an ELA paradigm of maternal separation and early weaning (MSEW) or control rearing. We found that mice with intact adult neurogenesis showed no behavioral changes in response to MSEW. After reducing adult neurogenesis, however, male mice previously subjected to MSEW had an unexpected decrease in avoidance behavior. This finding was not observed in female mice, suggesting that a sex difference exists in the role of adult-born neurons in buffering against ELA-induced changes in behavior. Taken together with the existing literature on ELA and avoidance behavior, this work suggests that strain differences exist in susceptibility to ELA and that adult-born neurons may play a role in regulating adaptive behavior.

Developmental Trajectories of Anhedonia in Preclinical Models

This chapter discusses how the complex concept of anhedonia can be operationalized and studied in preclinical models. It provides information about the development of anhedonia in the context of early-life adversity, and the power of preclinical models to tease out the diverse molecular, epigenetic, and network mechanisms that are responsible for anhedonia-like behaviors.Specifically, we first discuss the term anhedonia, reviewing the conceptual components underlying reward-related behaviors and distinguish anhedonia pertaining to deficits in motivational versus consummatory behaviors. We then describe the repertoire of experimental approaches employed to study anhedonia-like behaviors in preclinical models, and the progressive refinement over the past decade of both experimental instruments (e.g., chemogenetics, optogenetics) and conceptual constructs (salience, valence, conflict). We follow with an overview of the state of current knowledge of brain circuits, nodes, and projections that execute distinct aspects of hedonic-like behaviors, as well as neurotransmitters, modulators, and receptors involved in the generation of anhedonia-like behaviors. Finally, we discuss the special case of anhedonia that arises following early-life adversity as an eloquent example enabling the study of causality, mechanisms, and sex dependence of anhedonia.Together, this chapter highlights the power, potential, and limitations of using preclinical models to advance our understanding of the origin and mechanisms of anhedonia and to discover potential targets for its prevention and mitigation.

Single-Cell Transcriptional Changes in Hypothalamic Corticotropin-Releasing Factor-Expressing Neurons After Early-Life Adversity Inform Enduring Alterations in Vulnerabilities to Stress

Background

Mental health and vulnerabilities to neuropsychiatric disorders involve the interplay of genes and environment, particularly during sensitive developmental periods. Early-life adversity (ELA) and stress promote vulnerabilities to stress-related affective disorders, yet it is unknown how transient ELA dictates lifelong neuroendocrine and behavioral reactions to stress. The population of hypothalamic corticotropin-releasing factor (CRF)-expressing neurons that regulate stress responses is a promising candidate to mediate the long-lasting influences of ELA on stress-related behavioral and hormonal responses via enduring transcriptional and epigenetic mechanisms.

Methods

Capitalizing on a well-characterized model of ELA, we examined ELA-induced changes in gene expression profiles of CRF-expressing neurons in the hypothalamic paraventricular nucleus of developing male mice. We used single-cell RNA sequencing on isolated CRF-expressing neurons. We determined the enduring functional consequences of transcriptional changes on stress reactivity in adult ELA mice, including hormonal responses to acute stress, adrenal weights as a measure of chronic stress, and behaviors in the looming shadow threat task.

Results

Single-cell transcriptomics identified distinct and novel CRF-expressing neuronal populations, characterized by both their gene expression repertoire and their neurotransmitter profiles. ELA-provoked expression changes were selective to specific subpopulations and affected genes involved in neuronal differentiation, synapse formation, energy metabolism, and cellular responses to stress and injury. Importantly, these expression changes were impactful, apparent from adrenal hypertrophy and augmented behavioral responses to stress in adulthood.

Conclusions

We uncover a novel repertoire of stress-regulating CRF cell types differentially affected by ELA and resulting in augmented stress vulnerability, with relevance to the origins of stress-related affective disorders.

The adjuvant aluminum fate - Metabolic tale based on the basics of chemistry and biochemistry

Aluminum is inevitable component of many vaccines. The benefit of the vaccines is undeniable but effects of aluminum toxicity might be underestimated and neglected. In this review, we highlighted the mechanims of aluminum toxicity, which is still in debate. So far, all the papers that disscused the adverse aluminum effects pointed two mechanisms responsible for Al toxicity, direct Al toxicity and aluminum induced cell damage via the oxidative metabolism. According to our knowledge, which is based on basic principles of biochemistry and inorganic chemistry, we suggested that aluminum highly interferes with iron metabolism eventually resulting in iron-mediated cell damage. More importantly, in this paper, we offered easily feasible solutions, in order to avoid aluminum toxicity in the future. We suggest that as it once was, Calcium Phosphate again to be used as the adjuvant or better solution that the vaccine adjuvants should be based on zinc compounds or even better would be non-metal adjuvants, such as microcrystalline tyrosine and monosodium urate. Until an adequate adjuvant is provided, we suggest instant postponement of vaccination with vaccines which use aluminum as the adjuvant until the 12 months of age.

Prenatal maternal stress and autistic-like behaviours in Chinese preschoolers

Exposure to prenatal maternal stress (PNMS) has been implicated as a risk factor for a range of psychiatric disorders in children. However, there have been a few studies showing inconsistent associations between PNMS and offspring autistic-like behaviours. We therefore aimed to examine whether trimester-specific PNMS exposure might be related to an increased risk of autistic-like behaviours among preschoolers. Using data from Longhua Children Cohort Study, mothers of 65,931 preschool children were asked to recall their level of PNMS in each of the three trimesters of pregnancy, while children's current autistic-like behaviours were assessed using the Autism Behaviour Checklist. A series of Cox regression models were fitted to assess the association between PNMS exposure and autistic-like behaviours. After adjusting for potential confounders, the Cox regression models showed that PNMS exposure, especially during the second pregnant trimester, was significantly and positively associated with the presence of children's autistic-like behaviours. The strength of these associations was enhanced with the increase of PNMS exposure level. Furthermore, based on different permutations of exposure versus no exposure in each trimester, the participants were divided into eight groups. A cross-over analysis confirmed the aforementioned finding that the second pregnant trimester might be the sensitive period for PNMS exposure increasing the risk of autistic-like behaviours. Our findings supported the hypothesis of an association between PNMS exposure and autistic-like behaviours among preschoolers. Preventive interventions should be trialled to examine whether minimizing maternal psychological stress during pregnancy, especially the second trimester, may reduce the risk of offspring autistic-like behaviours.

Early Life Febrile Seizures Impair Hippocampal Synaptic Plasticity in Young Rats

Febrile seizures (FSs) in early life are significant risk factors of neurological disorders and cognitive impairment in later life. However, existing data about the impact of FSs on the developing brain are conflicting. We aimed to investigate morphological and functional changes in the hippocampus of young rats exposed to hyperthermia-induced seizures at postnatal day 10. We found that FSs led to a slight morphological disturbance. The cell numbers decreased by 10% in the CA1 and hilus but did not reduce in the CA3 or dentate gyrus areas. In contrast, functional impairments were robust. Long-term potentiation (LTP) in CA3-CA1 synapses was strongly reduced, which we attribute to the insufficient activity of N-methyl-D-aspartate receptors (NMDARs). Using whole-cell recordings, we found higher desensitization of NMDAR currents in the FS group. Since the desensitization of NMDARs depends on subunit composition, we analyzed NMDAR current decays and gene expression of subunits, which revealed no differences between control and FS rats. We suggest that an increased desensitization is due to insufficient activation of the glycine site of NMDARs, as the application of D-serine, the glycine site agonist, allows the restoration of LTP to a control value. Our results reveal a new molecular mechanism of FS impact on the developing brain.

Effects of early noise exposure on hippocampal-dependent behaviors during adolescence in male rats: influence of different housing conditions

Central nervous system (CNS) development is a very complex process that can be altered by environmental stimuli such as noise, which can generate long-term auditory and/or extra-auditory impairments. We have previously reported that early noise exposure can induce hippocampus-related behavioral alterations in postnatal day (PND) 28 adolescent rats. Furthermore, we recently found biochemical modifications in the hippocampus (HC) of these animals that seemed to endure even in more mature animals (i.e. PND35) and that have not been studied along with behavioral correlates. Thus, the aim of this work was to reveal novel data about the effects of early noise exposure on hippocampal-dependent behaviors in more mature animals. Additionally, extended enriched environment (EE) housing was evaluated to determine its capacity to induce behavioral modifications, either by its neuroprotective ability or the greater stimulation that it generates. Male Wistar rats were exposed to different noise schemes at PND7 or PND15. Upon weaning, some animals were transferred to EE whereas others were kept in standard cages. At PND35, different hippocampal-dependent behavioral assessments were performed. Results showed noise-induced behavioral changes that differed according to the scheme and age of exposure used. In addition, housing in an EE was effective either in preventing some of these changes or in inducing the appearance of new behavioral modifications. These findings suggest that CNS development would be sensitive to the effects of different type of environmental stimuli such as noise or enriched housing, leading to maladaptive behavioral changes that last even until adolescence.

Insects Provide Unique Systems to Investigate How Early-Life Experience Alters the Brain and Behavior

Early-life experiences have strong and long-lasting consequences for behavior in a surprising diversity of animals. Determining which environmental inputs cause behavioral change, how this information becomes neurobiologically encoded, and the functional consequences of these changes remain fundamental puzzles relevant to diverse fields from evolutionary biology to the health sciences. Here we explore how insects provide unique opportunities for comparative study of developmental behavioral plasticity. Insects have sophisticated behavior and cognitive abilities, and they are frequently studied in their natural environments, which provides an ecological and adaptive perspective that is often more limited in lab-based vertebrate models. A range of cues, from relatively simple cues like temperature to complex social information, influence insect behavior. This variety provides experimentally tractable opportunities to study diverse neural plasticity mechanisms. Insects also have a wide range of neurodevelopmental trajectories while sharing many developmental plasticity mechanisms with vertebrates. In addition, some insects retain only subsets of their juvenile neuronal population in adulthood, narrowing the targets for detailed study of cellular plasticity mechanisms. Insects and vertebrates share many of the same knowledge gaps pertaining to developmental behavioral plasticity. Combined with the extensive study of insect behavior under natural conditions and their experimental tractability, insect systems may be uniquely qualified to address some of the biggest unanswered questions in this field.

Long term effects of early life stress on HPA circuit in rodent models

Adaptation to environmental challenges represents a critical process for survival, requiring the complex integration of information derived from both external cues and internal signals regarding current conditions and previous experiences. The Hypothalamic-pituitary-adrenal axis plays a central role in this process inducing the activation of a neuroendocrine signaling cascade that affects the delicate balance of activity and cross-talk between areas that are involved in sensorial, emotional, and cognitive processing such as the hippocampus, amygdala, Prefrontal Cortex, Ventral Tegmental Area, and dorsal raphe. Early life stress, especially early critical experiences with caregivers, influences the functional and structural organization of these areas, affects these processes in a long-lasting manner and may result in long-term maladaptive and psychopathological outcomes, depending on the complex interaction between genetic and environmental factors. This review summarizes the results of studies that have modeled this early postnatal stress in rodents during the first 2 postnatal weeks, focusing on the long-term effects on molecular and structural alteration in brain areas involved in Hypothalamic-pituitary-adrenal axis function. Moreover, a brief investigation of epigenetic mechanisms and specific genetic targets mediating the long-term effects of these early environmental manipulations and at the basis of differential neurobiological and behavioral effects during adulthood is provided.

Noise-induced hippocampal oxidative imbalance and aminoacidergic neurotransmitters alterations in developing male rats: Influence of enriched environment during adolescence

Living in big cities might involuntarily expose people to high levels of noise causing auditory and/or extra-auditory impairments, including adverse effects on central nervous system (CNS) areas such as the hippocampus. In particular, CNS development is a very complex process that can be altered by environmental stimuli. We have previously shown that noise exposure of developing rats can induce hippocampal-related behavioral alterations. However, noise-induced biochemical alterations had not been studied yet. Thus, the aim of this work was to assess whether early noise exposure can affect rat hippocampal oxidative state and aminoacidergic neurotransmission tone. Additionally, the effectiveness of an enriched environment (EE) as a neuroprotective strategy was evaluated. Male Wistar rats were exposed to different noise schemes at 7 or 15 days after birth. Upon weaning, some animals were transferred to an EE whereas others were kept in standard cages. Short- and long-term measurements were performed to evaluate reactive oxygen species, thioredoxins levels and catalase activity as indicators of hippocampal oxidative status as well as glutamic acid decarboxylase and a subtype of glutamate transporter to evaluate aminoacidergic neurotransmission tone. Results showed noise-induced changes in hippocampal oxidative state and aminoacidergic neurotransmission markers that lasted until adolescence and differed according to the scheme and the age of exposure. Finally, EE housing was effective in preventing some of these changes. These findings suggest that CNS development seems to be sensitive to the effects of stressors such as noise, as well as those of an environmental stimulation, favoring prompt and lasting molecular changes.

Long-term effects of pre-gestational stress and perinatal venlafaxine treatment on neurobehavioral development of female offspring

Preclinical studies suggest that stress-related disorders even prior gestation can cause long-term changes at the level of neurobehavioral adaptations. Therefore, it is critical to consider undergoing antidepressant therapy which could reverse the negative consequences in the offspring. Venlafaxine is widely used in clinical practice; however insufficient amount of well-controlled studies verified the safety of venlafaxine therapy during gestation and lactation. The aim of this work was to investigate the effects of perinatal venlafaxine therapy on selected neurobehavioral variables in mothers and their female offspring using a model of maternal adversity. Pre-gestational stressed and non-stressed Wistar rat dams were treated with either venlafaxine (10 mg/kg/day) or vehicle during pregnancy and lactation. We have shown that pre-gestational stress decreased the number of pups with a significant reduction in the number of males but not females. Furthermore, we found that offspring of stressed and treated mothers exhibited anxiogenic behavior in juvenile and adolescent age. However, during adulthood pre-gestational stress significantly increased anxiety-like behavior of female, with venlafaxine treatment normalizing the state to control levels. Additionally, we found that even maternal stress prior gestation can have long-term impact on adult number of hippocampal immature neurons of the female offspring. A number of questions related to the best treatment options for maternal depression still remains, however present data may provide greater insight into the possible outcomes associated with perinatal venlafaxine therapy.

Cold stress modulates redox signalling in murine fresh bone marrow cells and promotes osteoclast transformation

Context: Alteration of redox signalling and RANK-L expression in FBMCs of mice exposed to different intensities of cold stress (15 °C, 8 °C and 4 °C) were studied.Objective: To understand the effects of varying intensities of cold stress on murine FBMCs and its impact on osteoclastogenesis.Materials and methods: FBMCs were isolated from mice exposed to different intensities of cold stress and used for immunoblotting and biochemical assays. Bone histometry was also done.Results: Different intensities of cold stress perturb redox signalling in FBMCs and alters bone histometry. Higher RANK-L expressions were noted in FBMCs of mice exposed to 8 °C and 4 °C as compared with 15 °C.Discussion and conclusion: Cold stress boosts free radical production in FBMC's, which might enhance RANK-L expression, an indicator of osteoclastogenesis. Thus, we speculate that stronger cold stress (8 °C and 4 °C) contributes to the development of early bone loss.

Neurodevelopmental Optimization after Early-Life Adversity: Cross-Species Studies to Elucidate Sensitive Periods and Brain Mechanisms to Inform Early Intervention

Human brain development is influenced by early-life experiences, particularly during sensitive periods, with impact on cognitive and emotional outcomes. Understanding how the timing and nature of such experiences (including adversity, trauma, and enrichment) govern their influence on brain organization is crucial for harnessing key environmental factors early in life to enhance brain development. Here we synthesize findings from human and animal studies focusing on sensitive periods and their regional and circuit specificity and highlight the challenge and power of such cross-species approaches in informing the 'next steps' to optimize cognitive and emotional health in developing children. We propose designs for neurodevelopmental optimization research programs utilizing randomized enhancement trials in early childhood to inform public health strategies on prevention and early intervention.

Modeling epileptic spasms during infancy: Are we heading for the treatment yet?

Infantile spasms (IS or epileptic spasms during infancy) were first described by Dr. William James West (aka West syndrome) in his own son in 1841. While rare by definition (occurring in 1 per 3200-3400 live births), IS represent a major social and treatment burden. The etiology of IS varies - there are many (>200) different known pathologies resulting in IS and still in about one third of cases there is no obvious reason. With the advancement of genetic analysis, role of certain genes (such as ARX or CDKL5 and others) in IS appears to be important. Current treatment strategies with incomplete efficacy and serious potential adverse effects include adrenocorticotropin (ACTH), corticosteroids (prednisone, prednisolone) and vigabatrin, more recently also a combination of hormones and vigabatrin. Second line treatments include pyridoxine (vitamin B6) and ketogenic diet. Additional treatment approaches use rapamycin, cannabidiol, valproic acid and other anti-seizure medications. Efficacy of these second line medications is variable but usually inferior to hormonal treatments and vigabatrin. Thus, new and effective models of this devastating condition are required for the search of additional treatment options as well as for better understanding the mechanisms of IS. Currently, eight models of IS are reviewed along with the ideas and mechanisms behind these models, drugs tested using the models and their efficacy and usefulness. Etiological variety of IS is somewhat reflected in the variety of the models. However, it seems that for finding precise personalized approaches, this variety is necessary as there is no "one-size-fits-all" approach possible for both IS in particular and epilepsy in general.

A Unique Mouse Model of Early Life Exercise Enables Hippocampal Memory and Synaptic Plasticity

Physical exercise is a powerful modulator of learning and memory. Mechanisms underlying the cognitive benefits of exercise are well documented in adult rodents. Exercise studies targeting postnatal periods of hippocampal maturation (specifically targeting periods of synaptic reorganization and plasticity) are lacking. We characterize a model of early-life exercise (ELE) in male and female mice designed with the goal of identifying critical periods by which exercise may have a lasting impact on hippocampal memory and synaptic plasticity. Mice freely accessed a running wheel during three postnatal periods: the 4^th postnatal week (juvenile ELE, P21–27), 6^th postnatal week (adolescent ELE, P35–41), or 4^th-6^th postnatal weeks (juvenile-adolescent ELE, P21–41). All exercise groups increased their running distances during ELE. When exposed to a subthreshold learning stimulus, juv ELE and juv-adol ELE formed lasting long-term memory for an object location memory task, whereas sedentary and adol ELE mice did not. Electrophysiological experiments revealed enhanced long-term potentiation in hippocampal CA1 in the juvenile-adolescent ELE group. I/O curves were also significantly modulated in all mice that underwent ELE. Our results suggest that early-life exercise, specifically during the 4^th postnatal week, can enable hippocampal memory, synaptic plasticity, and alter hippocampal excitability when occurring during postnatal periods of hippocampal maturation.

Prenatal alcohol exposure in the second trimester-equivalent increases the seizure susceptibility in developing rats

We have previously reported that prenatal alcohol exposure (PAE) in the 2nd trimester-equivalent of gestation is associated with increased N-methyl-d-aspartate (NMDA)-induced generalized tonic-clonic seizures (GTCSs) prevalence in postpartum developing rats. Whether the 1st trimester-equivalent of gestation is also a vulnerable period for developing GTCSs following PAE is unknown. Here, we investigated the effects of a single episode of PAE at embryonic day 8 (E8, in the 1st trimester-equivalent) or E18 (in the 2nd trimester-equivalent) on NMDA-induced seizures in developing rats at postnatal day 7 (P7, the equivalent of preterm newborns) and P15 (the equivalent of term infants). Pregnant Sprague-Dawley rats were given a single oral dose of ethanol (5 g/kg body weight) at E8 or E18 and the postpartum rats were tested for the susceptibility to NMDA-induced seizures at either P7 or P15. NMDA-induced seizures consisted of wild running-like behavior (WRLB), flexion seizures (FSs), clonic seizures (CSs), GTCSs, and tonic seizures (TSs); these seizures were observed in both control-treated and PAE-treated, male and female, P7 and P15 rats. Quantification reveals that the overall prevalence of CSs, GTCSs and TSs occurrence were significantly increased in the E18-PAE group compared to E8-PAE group, adjusting for sex and postnatal day. Furthermore, the overall prevalence of FSs and TSs occurrence was significantly increased in PAE-treated males compared to females, adjusting for embryonic stage and postnatal day. The overall prevalence of WRLB and FSs occurrence was also increased in PAE-P7 rats compared to PAE-P15 rats, adjusting for sex and embryonic stage. We conclude that the susceptibility to develop GTCSs was higher when PAE occurred in the 2nd rather than in the 1st trimester-equivalent of gestation.

Plasticity of the Reward Circuitry After Early-Life Adversity: Mechanisms and Significance

Disrupted operation of the reward circuitry underlies many aspects of affective disorders. Such disruption may manifest as aberrant behavior including risk taking, depression, anhedonia, and addiction. Early-life adversity is a common antecedent of adolescent and adult affective disorders involving the reward circuitry. However, whether early-life adversity influences the maturation and operations of the reward circuitry, and the potential underlying mechanisms, remain unclear. Here, we present novel information using cutting-edge technologies in animal models to dissect out the mechanisms by which early-life adversity provokes dysregulation of the complex interactions of stress and reward circuitries. We propose that certain molecularly defined pathways within the reward circuitry are particularly susceptible to early-life adversity. We examine regions and pathways expressing the stress-sensitive peptide corticotropin-releasing factor (CRF), which has been identified in critical components of the reward circuitry and interacting stress circuits. Notably, CRF is strongly modulated by early-life adversity in several of these brain regions. Focusing on amygdala nuclei and their projections, we provide evidence suggesting that aberrant CRF expression and function may underlie augmented connectivity of the nucleus accumbens with fear/anxiety regions, disrupting the function of this critical locus of pleasure and reward.

Developmental decrease in parvalbumin-positive neurons precedes increase in flurothyl-induced seizure susceptibility in the Brd2+/- mouse model of juvenile myoclonic epilepsy

OBJECTIVE

BRD2 is a human gene repeatedly linked to and associated with juvenile myoclonic epilepsy (JME). Here, we define the developmental stage when increased seizure susceptibility first manifests in heterozygous Brd2+/- mice, an animal model of JME. We wanted to determine (1) whether seizure susceptibility correlates with the proven decrease of γ-aminobutyric acidergic (GABAergic) neuron numbers and (2) whether the seizure phenotype can be affected by sex hormones.

METHODS

Heterozygous (Brd2+/-) and wild-type (wt) mice of both sexes were tested for flurothyl-induced seizure susceptibility at postnatal day 15 (P15; wt, n = 13; Brd2+/-, n = 20), at P30 (wt, n = 20; Brd2+/-, n = 20), and in adulthood (5-6 months of age; wt, n = 10; Brd2+/-, n = 12). We measured latency to clonic and tonic-clonic seizure onset (flurothyl threshold). We also compared relative density of parvalbumin-positive (PVA+) and GAD67+ GABA neurons in the striatum and primary motor (M1) neocortex of P15 (n = 6-13 mice per subgroup) and P30 (n = 7-10 mice per subgroup) mice. Additional neonatal Brd2+/- mice were injected with testosterone propionate (females) or formestane (males) and challenged with flurothyl at P30.

RESULTS

P15 Brd2+/- mice showed no difference in seizure susceptibility compared to P15 wt mice. However, even at this early age, Brd2+/- mice showed fewer PVA+ neurons in the striatum and M1 neocortex. Compared to wt, the striatum in Brd2+/- mice showed an increased proportion of immature PVA+ neurons, with smaller cell bodies and limited dendritic arborization. P30 Brd2+/- mice displayed increased susceptibility to flurothyl-induced clonic seizures compared to wt. Both genotype and sex strongly influenced the density of PVA+ neurons in the striatum. Susceptibility to clonic seizures remained increased in adult Brd2+/- mice, and additionally there was increased susceptibility to tonic-clonic seizures. In P30 females, neonatal testosterone reduced the number of flurothyl-induced clonic seizures.

SIGNIFICANCE

A decrease in striatal PVA+ GABAergic neurons developmentally precedes the onset of increased seizure susceptibility and likely contributes to the expression of the syndrome.

Blocking CRH receptors in adults mitigates age-related memory impairments provoked by early-life adversity

In humans, early-life adversity is associated with impairments in learning and memory that may emerge later in life. In rodent models, early-life adversity directly impacts hippocampal neuron structure and connectivity with progressive deficits in long-term potentiation and spatial memory function. Previous work has demonstrated that augmented release and actions of the stress-activated neuropeptide, CRH, contribute to the deleterious effects of early-life adversity on hippocampal dendritic arborization, synapse number and memory-function. Early-life adversity increases hippocampal CRH expression, and blocking hippocampal CRH receptor type-1 (CRHR1) immediately following early-life adversity prevented the consequent memory and LTP defects. Here, we tested if blocking CRHR1 in young adults ameliorates early-life adversity-provoked memory deficits later in life. A weeklong course of a CRHR1 antagonist in 2-month-old male rats prevented early-life adversity-induced deficits in object recognition memory that emerged by 12 months of age. Surprisingly, whereas the intervention did not mitigate early-life adversity-induced spatial memory losses at 4 and 8 months, it restored hippocampus-dependent location memory in 12-month-old rats that experienced early-life adversity. Neither early-life adversity nor CRHR1 blockade in the adult influenced anxiety- or depression-related behaviors. Altogether, these findings suggest that cognitive deficits attributable to adversity during early-life-sensitive periods are at least partially amenable to interventions later in life.

Infantile Spasms: An Update on Pre-Clinical Models and EEG Mechanisms

Infantile spasms (IS) is an epileptic encephalopathy with unique clinical and electrographic features, which affects children in the middle of the first year of life. The pathophysiology of IS remains incompletely understood, despite the heterogeneity of IS etiologies, more than 200 of which are known. In particular, the neurobiological basis of why multiple etiologies converge to a relatively similar clinical presentation has defied explanation. Treatment options for this form of epilepsy, which has been described as “catastrophic” because of the poor cognitive, developmental, and epileptic prognosis, are limited and not fully effective. Until the pathophysiology of IS is better clarified, novel treatments will not be forthcoming, and preclinical (animal) models are essential for advancing this knowledge. Here, we review preclinical IS models, update information regarding already existing models, describe some novel models, and discuss exciting new data that promises to advance understanding of the cellular mechanisms underlying the specific EEG changes seen in IS—interictal hypsarrhythmia and ictal electrodecrement.

Early-life adversity and neurological disease: age-old questions and novel answers

Neurological illnesses, including cognitive impairment, memory decline and dementia, affect over 50 million people worldwide, imposing a substantial burden on individuals and society. These disorders arise from a combination of genetic, environmental and experiential factors, with the latter two factors having the greatest impact during sensitive periods in development. In this Review, we focus on the contribution of adverse early-life experiences to aberrant brain maturation, which might underlie vulnerability to cognitive brain disorders. Specifically, we draw on recent robust discoveries from diverse disciplines, encompassing human studies and experimental models. These discoveries suggest that early-life adversity, especially in the perinatal period, influences the maturation of brain circuits involved in cognition. Importantly, new findings suggest that fragmented and unpredictable environmental and parental signals comprise a novel potent type of adversity, which contributes to subsequent vulnerabilities to cognitive illnesses via mechanisms involving disordered maturation of brain 'wiring'.

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.

Construction and disruption of spatial memory networks during development

Spatial memory, the aspect of memory involving encoding and retrieval of information regarding one's environment and spatial orientation, is a complex biological function incorporating multiple neuronal networks. Hippocampus-dependent spatial memory is not innate and emerges during development in both humans and rodents. In children, nonhippocampal dependent egocentric (self-to-object) memory develops before hippocampal-dependent allocentric (object-to-object) memory. The onset of allocentric spatial memory abilities in children around 22 mo of age occurs at an age-equivalent time in rodents when spatially tuned grid and place cells arise from patterned activity propagating through the entorhinal-hippocampal circuit. Neuronal activity, often driven by specific sensory signals, is critical for the normal maturation of brain circuits This patterned activity fine-tunes synaptic connectivity of the network and drives the emergence of specific firing necessary for spatial memory. Whereas normal activity patterns are required for circuit maturation, aberrant neuronal activity during development can have major adverse consequences, disrupting the development of spatial memory. Seizures during infancy, involving massive bursts of synchronized network activity, result in impaired spatial memory when animals are tested as adolescents or adults. This impaired spatial memory is accompanied by alterations in spatial and temporal coding of place cells. The molecular mechanisms by which early-life seizures lead to disruptions at the cellular and network levels are now becoming better understood, and provide a target for intervention, potentially leading to improved cognitive outcome in individuals experiencing early-life seizures.

Functional brain connectivity in a rodent seizure model of autistic-like behavior

OBJECTIVE

There is increasing evidence that Autism Spectrum Disorder (ASD) is a disorder of functional connectivity with both human and rodent studies demonstrating alterations in connectivity. Here, we hypothesized that early-life seizures (ELS) in rats would interrupt normal brain connectivity and result in autistic-like behavior (ALB).

METHODS

Following 50 seizures, adult rats were tested in the social interaction and social novelty tests and then underwent qualitative and quantitative intracranial electroencephalography (EEG) monitoring in the medial prefrontal cortex (PFC) and the hippocampal subfields, CA3 and CA1.

RESULTS

Rats with ELS showed deficits in social interaction and novelty, and compared with control, rats had marked increases in coherence within the hippocampus (CA3-CA1) and between the hippocampus and PFC during the awake and sleep states indicating hyperconnectivity. In addition, sleep spindle density was significantly reduced in rats with ELS. There were no differences in voltage correlations and power spectral densities between the ELS and control rats in any bandwidths.

CONCLUSION

Taken together, these findings indicate that ELS can result in ALB and alter functional connectivity as measured by coherence and sleep spindle density. These findings implicate altered connectivity as a robust neural signature for ALB following ELS.

Dysregulation of Neuronal Genes by Fetal-Neonatal Iron Deficiency Anemia Is Associated with Altered DNA Methylation in the Rat Hippocampus

Early-life iron deficiency results in long-term abnormalities in cognitive function and affective behavior in adulthood. In preclinical models, these effects have been associated with long-term dysregulation of key neuronal genes. While limited evidence suggests histone methylation as an epigenetic mechanism underlying gene dysregulation, the role of DNA methylation remains unknown. To determine whether DNA methylation is a potential mechanism by which early-life iron deficiency induces gene dysregulation, we performed whole genome bisulfite sequencing to identify loci with altered DNA methylation in the postnatal day (P) 15 iron-deficient (ID) rat hippocampus, a time point at which the highest level of hippocampal iron deficiency is concurrent with peak iron demand for axonal and dendritic growth. We identified 229 differentially methylated loci and they were mapped within 108 genes. Among them, 63 and 45 genes showed significantly increased and decreased DNA methylation in the P15 ID hippocampus, respectively. To establish a correlation between differentially methylated loci and gene dysregulation, the methylome data were compared to our published P15 hippocampal transcriptome. Both datasets showed alteration of similar functional networks regulating nervous system development and cell-to-cell signaling that are critical for learning and behavior. Collectively, the present findings support a role for DNA methylation in neural gene dysregulation following early-life iron deficiency.