Hyperactivation of the amygdala correlates with impaired social play behavior of prepubertal male rats in a maternal immune activation model

Postnatal Allergic Inhalation Induces Glial Inflammation in the Olfactory Bulb and Leads to Autism-Like Traits in Mice

Autism spectrum disorder (ASD) is one of the most prevalent neurodevelopmental disorders. To explore its pathophysiology, we investigated the association between neonatal allergic exposure and behavioral changes. Adult female C57BL/6J mice were immunized with adjuvant (aluminum hydroxide) or ovalbumin emulsified with adjuvant. After immunization, the mice were mated, and offspring were born at full term. The postnatal dams and infants were then simultaneously exposed to an allergen (ovalbumin) or vehicle via inhalation. After weaning, behavioral testing and histopathological analyses were conducted on male offspring. Compared with the vehicle-exposed offspring, the ovalbumin-exposed offspring had decreased sociability and increased repetitive behavior, thus representing an ASD-like phenotype in mice. Moreover, histopathological analyses revealed that the ovalbumin-exposed mice had increased astroglial, microglial, and eosinophilic infiltration in the olfactory bulb, as well as increased eosinophils in the nasal mucosa. The ovalbumin-exposed mice also had decreased dendritic spine density and a lower proportion of mature spines, suggesting the impairment of stimulus-induced synaptogenesis. In conclusion, postnatal allergic exposure induced an ASD-like phenotype, as well as allergic rhinitis, which was followed by glial inflammation in the olfactory bulb parenchyma.

R-Baclofen Treatment Corrects Autistic-like Behavioral Deficits in the RjIbm(m):FH Fawn-Hooded Rat Strain

The Fawn-hooded rat has long been used as a model for various peripheral and central disorders and the data available indicate that the social behavior of this strain may be compromised. However, a thorough description of the Fawn-hooded rat is unavailable in this regard. The objective of the present study was to investigate various aspects of the Fawn-hooded rat's social behavior in depth. Our results show that several facets of socio-communicational behavior are impaired in the RjIbm(m):FH strain, including defective ultrasonic vocalizations in pups upon maternal deprivation, reduced social play in adolescence and impaired social novelty discrimination in adulthood. In addition, Fawn-hooded rats exhibited heightened tactile sensitivity and hyperactivity. The defects observed were comparable to those induced by prenatal valproate exposure, a widely utilized model of autism spectrum disorder. Further on, the pro-social drug R-baclofen (0.25-1 mg/kg) reversed the autistic-like defects observed in Fawn-hooded rats, specifically the deficiency in ultrasonic vocalization, tactile sensitivity and social novelty discrimination endpoints. In conclusion, the asocial, hypersensitive and hyperactive phenotype as well as the responsivity to R-baclofen indicate this variant of the Fawn-hooded rat strain may serve as a model of autism spectrum disorder and could be useful in the identification of novel drug candidates.

Exposure to the psychedelic substance 25 H-NBOMe disrupts maternal care in lactating rats and subsequently impairs the social play behavior of the offspring

Given the critical role of maternal care in the neurodevelopment of offspring, this study aimed to investigate the effects of the psychedelic substance 25 H-NBOMe on maternal behavior in lactating rats and its subsequent impact on the social and neurodevelopmental behavior of the offspring. We administered two different dosages of 25 H-NBOMe (0.3 mg/kg and 1.0 mg/kg; i,p,) to lactating rats and observed changes in maternal behaviors, such as nest-building and pup retrieval, and in offspring behaviors, including social play. Behavioral assessments were complemented by physiological measurements to rule out general health or nutritional decline. 25 H-NBOMe significantly disrupted maternal behaviors, including nest-building and pup retrieval, without affecting the weight of dams or offspring. Offspring of exposed dams exhibited reduced social play behavior. Higher doses led to more pronounced disruptions, while lower doses, despite not visibly affecting maternal behavior, still impacted offspring behavior, suggesting potential direct effects of 25 H-NBOMe. The study highlights the potential risks associated with the use of 25 H-NBOMe during lactation, emphasizing its detrimental impact on maternal care and offspring development. These findings contribute to understanding the neurobiological effects of psychedelic substances during critical developmental periods and underscore the importance of avoiding their use.

Influence of maternal immune activation on autism-like symptoms and coping strategies in male offspring

Maternal immune activation (MIA) caused by exposure to pathogens or inflammation during critical periods of gestation increased susceptibility to neurodevelopmental disorders, including autism, in the offspring. In the present work, we aimed to provide characterization of the long-term consequences on anxiety-like behavior and cardiovascular stress response of MIA in the offspring. This study aimed to evaluate the effect of MIA by lipopolysaccharide (LPS) in adult male offspring. In our study, the animals were subjected to a range of behavioral and physiological tests, including the elevated plus maze, social interaction, cat odor response, open field behavior, contextual fear conditioning, and cardiovascular responses during restraint stress. In the offspring of MIA, our study unveiled distinct anxious behaviors. This was evident by fewer entries into the open arms of the maze, diminished anti-thigmotaxis in the open field, and a decrease in social interaction time. Moreover, these rats showed heightened sensitivity to cat odor, exhibited prolonged freezing during fear conditioning, and presented elevated 22 Hz ultrasonic vocalizations. Notably, during restraint stress, these animals manifested an augmented blood pressure response, and this was associated with an increase in c-fos expression in the locus coeruleus compared to the control group. These findings collectively underline the extensive behavioral and physiological alterations stemming from MIA. This study deepens our understanding of the significance of maternal health in predisposing offspring to neurobehavioral deficits and psychiatric disorders.

Therapeutic efficacy of sulforaphane in autism spectrum disorders and its association with gut microbiota: animal model and human longitudinal studies

Introduction

Sulforaphane (SFN) has been found to alleviate complications linked with several diseases by regulating gut microbiota (GM), while the effect of GM on SFN for autism spectrum disorders (ASD) has not been studied. Therefore, this study aimed to investigate the relationship between the effects of SFN on childhood ASD and GM through animal model and human studies.

Methods

We evaluated the therapeutic effects of SFN on maternal immune activation (MIA) induced ASD-like rat model and pediatric autism patients using three-chamber social test and OSU Autism Rating Scale-DSM-IV (OARS-4), respectively, with parallel GM analysis using 16SrRNA sequencing.

Results

SFN significantly improved the sniffing times of ASD-like rats in the three-chamber test. For human participants, the average verbal or non-verbal communication (OSU-CO) scores of SFN group had changed significantly at the 12-wk endpoint. SFN was safe and no serious side effects after taking. GM changes were similar for both ASD-like rats and ASD patients, such as consistent changes in order Bacillales, family Staphylococcaceae and genus Staphylococcus. Although the gut microbiota composition was significantly altered in SFN-treated ASD-like rats, the alteration of GM was not evident in ASD patients after 12 weeks of SFN treatment. However, in the network analysis, we found 25 taxa correlated with rats' social behavior, 8 of which were associated with SFN treatment in ASD-like rats, For ASD patients, we found 35 GM abundance alterations correlated with improvements in ASD symptoms after SFN treatment. Moreover, family Pasteurellaceae and genus Haemophilus were found to be associated with SFN administration in the network analyses in both ASD-like rats and ASD patients.

Discussion

These findings suggest that SFN could provide a novel avenue for preventing and treating ASD, and its therapeutic effects might be related to gut microbiota.

An enriched maternal environment and stereotypies of sows differentially affect the neuro-epigenome of brain regions related to emotionality in their piglets

Epigenetic mechanisms are important modulators of neurodevelopmental outcomes in the offspring of animals challenged during pregnancy. Pregnant sows living in a confined environment are challenged with stress and lack of stimulation which may result in the expression of stereotypies (repetitive behaviours without an apparent function). Little attention has been devoted to the postnatal effects of maternal stereotypies in the offspring. We investigated how the environment and stereotypies of pregnant sows affected the neuro-epigenome of their piglets. We focused on the amygdala, frontal cortex, and hippocampus, brain regions related to emotionality, learning, memory, and stress response. Differentially methylated regions (DMRs) were investigated in these brain regions of male piglets born from sows kept in an enriched vs a barren environment. Within the latter group of piglets, we compared the brain methylomes of piglets born from sows expressing stereotypies vs sows not expressing stereotypies. DMRs emerged in each comparison. While the epigenome of the hippocampus and frontal cortex of piglets is mainly affected by the maternal environment, the epigenome of the amygdala is mainly affected by maternal stereotypies. The molecular pathways and mechanisms triggered in the brains of piglets by maternal environment or stereotypies are different, which is reflected on the differential gene function associated to the DMRs found in each piglets' brain region . The present study is the first to investigate the neuro-epigenomic effects of maternal enrichment in pigs' offspring and the first to investigate the neuro-epigenomic effects of maternal stereotypies in the offspring of a mammal.

Neural Circuit Transitions Supporting Developmentally Specific Social Behavior

Environmentally appropriate social behavior is critical for survival across the lifespan. To support this flexible behavior, the brain must rapidly perform numerous computations taking into account sensation, memory, motor-control, and many other systems. Further complicating this process, individuals must perform distinct social behaviors adapted to the unique demands of each developmental stage; indeed, the social behaviors of the newborn would not be appropriate in adulthood and vice versa. However, our understanding of the neural circuit transitions supporting these behavioral transitions has been limited. Recent advances in neural circuit dissection tools, as well as adaptation of these tools for use at early time points, has helped uncover several novel mechanisms supporting developmentally appropriate social behavior. This review, and associated Minisymposium, bring together social neuroscience research across numerous model organisms and ages. Together, this work highlights developmentally regulated neural mechanisms and functional transitions in the roles of the sensory cortex, prefrontal cortex, amygdala, habenula, and the thalamus to support social interaction from infancy to adulthood. These studies underscore the need for synthesis across varied model organisms and across ages to advance our understanding of flexible social behavior.

The impact of social defeat on basomedial amygdala neuronal activity in adult male rats

Social stressors negatively impact social function, and this is mediated by the amygdala across species. Social defeat stress is an ethologically relevant social stressor in adult male rats that increases social avoidance, anhedonia, and anxiety-like behaviors. While amygdala manipulations can mitigate the negative effects of social stressors, the impact of social defeat on the basomedial subregion of the amygdala is relatively unclear. Understanding the role of the basomedial amygdala may be especially important, as prior work has demonstrated that it drives physiological responses to stress, including heart-rate related responses to social novelty. In the present study, we quantified the impact of social defeat on social behavior and basomedial amygdala neuronal responses using anesthetized in vivo extracellular electrophysiology. Socially defeated rats displayed increased social avoidance behavior towards novel Sprague Dawley conspecifics and reduced time initiating social interactions relative to controls. This effect was most pronounced in rats that displayed defensive, boxing behavior during social defeat sessions. We next found that socially defeated rats showed lower overall basomedial amygdala firing and altered the distribution of neuronal responses relative to the control condition. We separated neurons into low and high Hz firing groups, and neuronal firing was reduced in both low and high Hz groups but in a slightly different manner. This work demonstrates that basomedial amygdala activity is sensitive to social stress, displaying a distinct pattern of social stress-driven activity relative to other amygdala subregions.

Maternal immune activation alters social affective behavior and sensitivity to corticotropin releasing factor in male but not female rats

Prenatal infection increases risk for neurodevelopmental disorders such as autism in offspring. In rodents, prenatal administration of the viral mimic Polyinosinic: polycytidylic acid (Poly I: C) allows for investigation of developmental consequences of gestational sickness on offspring social behavior and neural circuit function. Because maternal immune activation (MIA) disrupts cortical development and sociability, we examined approach and avoidance in a rat social affective preference (SAP) task. Following maternal Poly I:C (0.5 mg/kg) injection on gestational day 12.5, male adult offspring (PN 60-64) exhibited atypical social interactions with stressed conspecifics whereas female SAP behavior was unaffected by maternal Poly I:C. Social responses to stressed conspecifics depend upon the insular cortex where corticotropin releasing factor (CRF) modulates synaptic transmission and SAP behavior. We characterized insular field excitatory postsynaptic potentials (fEPSP) in adult offspring of Poly I:C or control treated dams. Male MIA offspring showed decreased sensitivity to CRF (300 nM) while female MIA offspring showed greater sensitivity to CRF compared to sham offspring. These sex specific effects appear to be behaviorally relevant as CRF injected into the insula of male and female rats prior to social exploration testing had no effect in MIA male offspring but increased social interaction in female MIA offspring. We examined the cellular distribution of CRF receptor mRNA but found no effect of maternal Poly I:C in the insula. Together, these experiments reveal sex specific effects of prenatal infection on offspring responses to social affective stimuli and identify insular CRF signaling as a novel neurobiological substrate for autism risk.

Characterizing maternal isolation-induced ultrasonic vocalizations in a gene-environment interaction rat model for autism

Deficits in social communication and language development belong to the earliest diagnostic criteria of autism spectrum disorders. Of the many risk factors for autism spectrum disorder, the contactin-associated protein-like 2 gene, CNTNAP2, is thought to be important for language development. The present study used a rat model to investigate the potential compounding effects of autism spectrum disorder risk gene mutation and environmental challenges, including breeding conditions or maternal immune activation during pregnancy, on early vocal communication in the offspring. Maternal isolation-induced ultrasonic vocalizations from Cntnap2 wildtype and knockout rats at selected postnatal days were analyzed for their acoustic, temporal and syntax characteristics. Cntnap2 knockout pups from heterozygous breeding showed normal numbers and largely similar temporal structures of ultrasonic vocalizations to wildtype controls, whereas both parameters were affected in homozygously bred knockouts. Homozygous breeding further exacerbated altered pitch and transitioning between call types found in Cntnap2 knockout pups from heterozygous breeding. In contrast, the effect of maternal immune activation on the offspring's vocal communication was confined to call type syntax, but left ultrasonic vocalization acoustic and temporal organization intact. Our results support the "double-hit hypothesis" of autism spectrum disorder risk gene-environment interactions and emphasize that complex features of vocal communication are a useful tool for identifying early autistic-like features in rodent models.

Sex Differences in Neurodevelopmental Disorders: A Key Role for the Immune System

Sex differences are prominent defining features of neurodevelopmental disorders. Understanding the sex biases in these disorders can shed light on mechanisms leading to relative risk and resilience for the disorders, as well as more broadly advance our understanding of how sex differences may relate to brain development. The prevalence of neurodevelopmental disorders is increasing, and the two most common neurodevelopmental disorders, Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD) exhibit male-biases in prevalence rates and sex differences in symptomology. While the causes of neurodevelopmental disorders and their sex differences remain to be fully understood, increasing evidence suggests that the immune system plays a critical role in shaping development. In this chapter we discuss sex differences in prevalence and symptomology of ASD and ADHD, review sexual differentiation and immune regulation of neurodevelopment, and discuss findings from human and rodent studies of immune dysregulation and perinatal immune perturbation as they relate to potential mechanisms underlying neurodevelopmental disorders. This chapter will give an overview of how understanding sex differences in neuroimmune function in the context of neurodevelopmental disorders could lend insight into their etiologies and better treatment strategies.

Perinatal exposure to glyphosate-based herbicides induced neurodevelopmental behaviors impairments and increased oxidative stress in the prefrontal cortex and hippocampus in offspring

Glyphosate is the organophosphate pesticide most widely used in the world. Recent studies correlate exposure to glyphosate and the emergence of neurodevelopmental disorders. Therefore, it was objective to propose a rat model of perinatal exposure to glyphosate-based herbicides (GBH) to study associated neurodevelopmental disorders. Behavioral aspects and brain pathways were assessed in the prepubertal phase. For this, maternal treatment occurred throughout the entire gestation period (from GD0) until weaning on postnatal day 22 (PND 22). Control group received oral gavage with 5 mL/kg of saline per day and GBH group received oral gavage with 50 mg/kg of GBH per day (n = 10 per group). Maternal behavior was evaluated in PND 2-6. Offspring were evaluated for quantification of ultrasonic vocalizations (PND 5); homing behavior test (PND 13); and hole board, social play behavior, open field, and object recognition tests (PND 28-32). Prefrontal cortex and hippocampus of the offspring were processed to evaluate oxidative stress. Maternal exposure to GBH impaired early social communication, olfactory discrimination, social play behavior, and the exploration of objects, in addition to increasing repetitive and stereotyped movements. GBH also increased oxidative stress. Therefore, perinatal GBH exposure induced behavioral and oxidative stress impairments in rats associated with neurodevelopmental disorders. The manifestations found in the offspring are in accordance with symptoms of autism spectrum disorder.

Impact of Maternal Immune Activation on Nonhuman Primate Prefrontal Cortex Development: Insights for Schizophrenia

Late adolescence is a period of dynamic change in the brain as humans learn to navigate increasingly complex environments. In particular, prefrontal cortical (PFC) regions undergo extensive remodeling as the brain is fine-tuned to orchestrate cognitive control over attention, reasoning, and emotions. Late adolescence also presents a uniquely vulnerable period as neurodevelopmental illnesses, such as schizophrenia, become evident and worsen into young adulthood. Challenges in early development, including prenatal exposure to infection, may set the stage for a cascade of maladaptive events that ultimately result in aberrant PFC connectivity and function before symptoms emerge. A growing body of research suggests that activation of the mother's immune system during pregnancy may act as a disease primer, in combination with other environmental and genetic factors, contributing to an increased risk of neurodevelopmental disorders, including schizophrenia. Animal models provide an invaluable opportunity to examine the course of brain and behavioral changes in offspring exposed to maternal immune activation (MIA). Although the vast majority of MIA research has been carried out in rodents, here we highlight the translational utility of the nonhuman primate (NHP) as a model species more closely related to humans in PFC structure and function. In this review, we consider the protracted period of brain and behavioral maturation in the NHP, describe emerging findings from MIA NHP offspring in the context of rodent preclinical models, and lastly explore the translational relevance of the NHP MIA model to expand understanding of the etiology and developmental course of PFC pathology in schizophrenia.

Advantages and Limitations of Animal Schizophrenia Models

Mental illness modeling is still a major challenge for scientists. Animal models of schizophrenia are essential to gain a better understanding of the disease etiopathology and mechanism of action of currently used antipsychotic drugs and help in the search for new and more effective therapies. We can distinguish among pharmacological, genetic, and neurodevelopmental models offering various neuroanatomical disorders and a different spectrum of symptoms of schizophrenia. Modeling schizophrenia is based on inducing damage or changes in the activity of relevant regions in the rodent brain (mainly the prefrontal cortex and hippocampus). Such artificially induced dysfunctions approximately correspond to the lesions found in patients with schizophrenia. However, notably, animal models of mental illness have numerous limitations and never fully reflect the disease state observed in humans.

The Changes of Amygdala Transcriptome in Autism Rat Model After Arginine Vasopressin Treatment

Background

Some studies have shown that arginine vasopressin (AVP) can significantly improve the social interaction disorder of autism, but the mechanism remains unclear.

Methods

Female Wistar rats were intraperitoneally injected with VPA or normal saline at embryonic day 12.5 to establish an autism model or normal control in their offspring. Male offspring prenatally exposed to VPA were randomly assigned to two groups: the VPA-induced autism model group and the AVP group. The rats in the AVP group were treated with intranasal AVP at postnatal day (PND) 21 and for 3 weeks. The VPA-induced autism model group was given the same dose of normal saline in the same way. Behavioral responses were evaluated in the open field and three-chambered social test apparatus; the expression levels of AVP in serum were detected by enzyme-linked immunosorbent assay kit, and the gene expression levels on the amygdala were measured by RNA-seq at PND42.

Results

Intranasal administration of AVP can significantly improve the social interaction disorder and elevate the levels of AVP in serum. Transcriptome sequencing results showed that 518 differently expressed genes (DEGs) were identified in the VPA-induced autism model group compared with the control in this study. Gene Ontology biological process enrichment analysis of DEGs showed that the VPA-induced autism model group had significant nervous system developmental impairments compared with the normal group, particularly in gliogenesis, glial cell differentiation, and oligodendrocyte differentiation. Gene Set Enrichment Analysis (GSEA) enrichment analysis also showed that biological process of oligodendrocyte differentiation, axoneme assembly, and axon ensheathment were inhibited in the VPA-induced autism model group. Pathway enrichment analysis of DEGs between the control and VPA-induced autism model group showed that the PI3K/AKT and Wnt pathways were significantly dysregulated in the VPA-induced autism model group. Few DEGs were found when compared with the transcriptome between the VPA-induced autism model group and the AVP treatment group. GSEA enrichment analysis showed deficits in oligodendrocyte development and function were significantly improved after AVP treatment; the pathways were mainly enriched in the NOTCH, mitogen-activated protein kinase, and focal adhesion signaling pathways, but not in the PI3K/AKT and Wnt pathways. The expression patterns analysis also showed the same results.

Conclusion

AVP can significantly improve the social interaction disorder of VPA-induced autism model, and AVP may target behavioral symptoms in autism by modulating the vasopressin pathways, rather than primary disease mechanisms.

Influence of Prenatal Drug Exposure, Maternal Inflammation, and Parental Aging on the Development of Autism Spectrum Disorder

Autism spectrum disorder (ASD) affects reciprocal social interaction and produces abnormal repetitive, restrictive behaviors and interests. The diverse causes of ASD are divided into genetic alterations and environmental risks. The prevalence of ASD has been rising for several decades, which might be related to environmental risks as it is difficult to consider that the prevalence of genetic disorders related to ASD would increase suddenly. The latter includes (1) exposure to medications, such as valproic acid (VPA) and selective serotonin reuptake inhibitors (SSRIs) (2), maternal complications during pregnancy, including infection and hypertensive disorders of pregnancy, and (3) high parental age. Epidemiological studies have indicated a pathogenetic role of prenatal exposure to VPA and maternal inflammation in the development of ASD. VPA is considered to exert its deleterious effects on the fetal brain through several distinct mechanisms, such as alterations of γ-aminobutyric acid signaling, the inhibition of histone deacetylase, the disruption of folic acid metabolism, and the activation of mammalian target of rapamycin. Maternal inflammation that is caused by different stimuli converges on a higher load of proinflammatory cytokines in the fetal brain. Rodent models of maternal exposure to SSRIs generate ASD-like behavior in offspring, but clinical correlations with these preclinical findings are inconclusive. Hypertensive disorders of pregnancy and advanced parental age increase the risk of ASD in humans, but the mechanisms have been poorly investigated in animal models. Evidence of the mechanisms by which environmental factors are related to ASD is discussed, which may contribute to the development of preventive and therapeutic interventions for ASD.