Subchronic treatment of donepezil rescues impaired social, hyperactive, and stereotypic behavior in valproic acid-induced animal model of autism

Sociability: Comparing the Effect of Chlorpyrifos with Valproic Acid

In recent years, exposures to organophosphate pesticide have been highlighted as a possible cause or aggravating factor of autism spectrum disorder (ASD). The present study examined if Wistar rats prenatally exposed to chlorpyrifos (CPF) at a dose of 1 mg/kg in GD 12.5-15.5 could express similar behaviors to those exposed to valproic acid (VPA, 400 mg/kg) during the same administration window, which is an accepted animal model of autism. The 3-chambered test was employed to evaluate sociability and reaction to social novelty in two experiments, the first in adolescence and the second in adulthood. The results obtained in this study show that animals prenatally treated with CPF or VPA show a similar behavioral phenotype compared to the control group (CNT). In adolescence, the CPF animals showed a negative index in the reaction to social novelty, followed closely by the VPA, while both experimental groups showed a recovery in this aspect during adulthood. This study therefore provides evidence to suggest that prenatal exposure to CPF in rats could have similar effects on certain components of sociability to those seen in autistic models.

[Assessment of developmental neurotoxicity of pharmaceuticals using zebrafish behavior]

Pharmaceuticals used for pregnant women must be safe for the babies while therapeutic to the mothers. To ensure the safety of drugs, developmental neurotoxicity should be evaluated although it is currently not a mandatory requirement in the US and Europe at the regulatory level. Organisation for Economic Co-operation and Development (OECD) has constituted the test guideline (TG426) to assess developmental neurotoxicity. TG426 requires various assessments using animals (assuming rats), including the brain weight, neuropathology, locomotion, sensorimotor function, and learning ability of dams from the mother treated with the chemical during pregnancy. Due to the huge burden of the cost, time, and labor, the number of chemicals evaluated for developmental neurotoxicity by TG426 remains around 200. To boost the pace of the assessment, OCED has constituted a novel guideline (No. 377) adopting in vitro test batteries. OCED has also evaluated the utility of the neurobehavior of zebrafish larvae in the assessment of developmental neurotoxicity. In this review, I focus on valproic acid, a therapeutic drug to treat epilepsy and bipolar disorder and a well-known developmental neurotoxicant, and summarize the studies using zebrafish neurobehavior to assess the developmental neurotoxicity of valproic acid. The utility and validity of zebrafish neurobehavior for developmental neurotoxicity testing are discussed by comparing the findings from rodents and humans.

Striatal Interneuron Imbalance in a Valproic Acid-Induced Model of Autism in Rodents Is Accompanied by Atypical Somatosensory Processing

Autism spectrum disorder (ASD) is characterized by deficits in social interaction and communication, cognitive rigidity, and atypical sensory processing. Recent studies suggest that the basal ganglia, specifically the striatum (NSt), plays an important role in ASD. While striatal interneurons, including cholinergic (ChAT+) and parvalbumin-positive (PV+) GABAergic neurons, have been described to be altered in animal models of ASD, their specific contribution remains elusive. Here, we combined behavioral, anatomical, and electrophysiological quantifications to explore if interneuron balance could be implicated in atypical sensory processing in cortical and striatal somatosensory regions of rats subjected to a valproic acid (VPA) model of ASD. We found that VPA animals showed a significant decrease in the number of ChAT+ and PV+ cells in multiple regions (including the sensorimotor region) of the NSt. We also observed significantly different sensory-evoked responses at the single-neuron and population levels in both striatal and cortical regions, as well as corticostriatal interactions. Therefore, selective elimination of striatal PV+ neurons only partially recapitulated the effects of VPA, indicating that the mechanisms behind the VPA phenotype are much more complex than the elimination of a particular neural subpopulation. Our results indicate that VPA exposure induced significant histological changes in ChAT+ and PV+ cells accompanied by atypical sensory-evoked corticostriatal population dynamics that could partially explain the sensory processing differences associated with ASD.

Reversal of electrophysiological and behavioral deficits mediated by 5-HT7 receptor upregulation following LP-211 treatment in an autistic-like rat model induced by prenatal valproic acid exposure

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by alterations and imbalances in multiple brain neurochemical systems, particularly the serotonergic neurotransmission. This includes changes in serotonin (5-HT) levels, aberrations in 5-HT transporter activity, and decreased synthesis and expression of 5-HT receptors (5-HT7Rs). The exact role of the brain 5-HT system in the development of ASD remains unclear, with conflicting evidence on its involvement. Recently, we have reported research has shown a significant decrease in serotonergic neurons originating from the raphe nuclei and projecting to the CA1 region of the dorsal hippocampus in autistic-like rats. Additionally, we have shown that chronic activation of 5-HT7Rs reverses the effects of autism induction on synaptic plasticity. However, the functional significance of 5-HT7Rs at the cellular level is still not fully understood. This study presents new evidence indicating an upregulation of 5-HT7R in the CA1 subregion of the hippocampus following the induction of autism. The present account also demonstrates that activation of 5-HT7R with its agonist LP-211 can reverse electrophysiological abnormalities in hippocampal pyramidal neurons in a rat model of autism induced by prenatal exposure to VPA. Additionally, in vivo administration of LP-211 resulted in improvements in motor coordination, novel object recognition, and a reduction in stereotypic behaviors in autistic-like offspring. The findings suggest that dysregulated expression of 5-HT7Rs may play a role in the pathophysiology of ASD, and that agonists like LP-211 could potentially be explored as a pharmacological treatment for autism spectrum disorder.

Low-frequency repetitive transcranial magnetic stimulation alleviates abnormal behavior in valproic acid rat model of autism through rescuing synaptic plasticity and inhibiting neuroinflammation

Autism is a complex neurodevelopmental disorder with no effective treatment available currently. Repetitive transcranial magnetic stimulation (rTMS) is emerging as a promising neuromodulation technique to treat autism. However, the mechanism how rTMS works remains unclear, which restrict the clinical application of magnetic stimulation in the autism treatment. In this study, we investigated the effect of low-frequency rTMS on the autistic-like symptoms and explored if this neuroprotective effect was associated with synaptic plasticity and neuroinflammation in the hippocampus. A rat model of autism was established by intraperitoneal injection of valproic acid (VPA) in pregnant rats and male offspring were treated with 1 Hz rTMS daily for two weeks continuously. Behavior tests were performed to identify behavioral abnormality. Synaptic plasticity was measured by in vivo electrophysiological recording and Golgi-Cox staining. Synapse and inflammation associated proteins were detected by immunofluorescence and Western blot analyses. Results showed prenatal VPA-exposed rats exhibited autistic-like and anxiety-like behaviors, and cognitive impairment. Synaptic plasticity deficits and the abnormality expression of synapse-associated proteins were found in the hippocampus of prenatal VPA-exposed rats. Prenatal VPA exposure increased the level of inflammation cytokines and promoted the excessive activation of microglia. rTMS significantly alleviated the prenatal VPA-induced abnormalities including behavioral and synaptic plasticity deficits, and excessive neuroinflammation. TMS maybe a potential strategy for autism therapy via rescuing synaptic plasticity and inhibiting neuroinflammation.

Black seed oil reverses chronic antibiotic-mediated depression and social behaviour deficits via modulation of hypothalamic mitochondrial-dependent markers and insulin expression

Chronic antibiotic use has been reported to impair mitochondrial indices, hypothalamus-mediated metabolic function, and amygdala-regulated emotional processes. Natural substances such as black seed (Nigella sativa) oil could be beneficial in mitigating these impairments. This study aimed to assess the impact of black seed oil (NSO) on depression and sociability indices, redox imbalance, mitochondrial-dependent markers, and insulin expression in mice subjected to chronic ampicillin exposure. Forty adult male BALB/c mice (30 ± 2 g) were divided into five groups: the CTRL group received normal saline, the ABT group received ampicillin, the NSO group received black seed oil, the ABT/NSO group concurrently received ampicillin and black seed oil, and the ABT+NSO group experienced pre-exposure to ampicillin followed by subsequent treatment with black seed oil. The ampicillin-exposed group exhibited depressive-like behaviours, impaired social interactive behaviours, and disruptions in mitochondrial-dependent markers in plasma and hypothalamic tissues, accompanied by an imbalance in antioxidant levels. Moreover, chronic antibiotic exposure downregulated insulin expression in the hypothalamus. However, these impairments were significantly ameliorated in the ABT/NSO, and ABT+NSO groups compared to the untreated antibiotic-exposed group. Overall, findings from this study suggest the beneficial role of NSO as an adjuvant therapy in preventing and abrogating mood behavioural and neural-metabolic impairments of chronic antibiotic exposure.

Long-Term Epigenetic Regulation of Foxo3 Expression in Neonatal Valproate-Exposed Rat Hippocampus with Sex-Related Differences

Perinatal exposure to valproic acid is commonly used for autism spectrum disorder (ASD) animal model development. The inhibition of histone deacetylases by VPA has been proposed to induce epigenetic changes during neurodevelopment, but the specific alterations in genetic expression underlying ASD-like behavioral changes remain unclear. We used qPCR-based gene expression and epigenetics tools and Western blotting in the hippocampi of neonatal valproic acid-exposed animals at 4 weeks of age and conducted the social interaction test to detect behavioral changes. Significant alterations in gene expression were observed in males, particularly concerning mRNA expression of Foxo3, which was significantly associated with behavioral changes. Moreover, notable differences were observed in H3K27ac chromatin immunoprecipitation, quantitative PCR (ChIP-qPCR), and methylation-sensitive restriction enzyme-based qPCR targeting the Foxo3 gene promoter region. These findings provide evidence that epigenetically regulated hippocampal Foxo3 expression may influence social interaction-related behavioral changes. Furthermore, identifying sex-specific gene expression and epigenetic changes in this model may elucidate the sex disparity observed in autism spectrum disorder prevalence.

Induction of autism-related behavior in male mice by early-life vitamin D deficiency: association with disruption of the gut microbial composition and homeostasis

Vitamin D deficiency (VDD) during early life emerges as a potential risk factor for autism spectrum disorder (ASD). Individuals with autism commonly exhibit lower vitamin D (VD) levels compared to the general population, and VD deficiency is prevalent during pregnancy and lactation. Moreover, gastrointestinal comorbidity, prevalent in ASD patients, correlates closely with disruptions in the gut microbiota and altered intestinal permeability. Therefore, it is fascinating and significant to explore the effects of maternal VD deficiency during pregnancy and lactation on the maturation of the gut microbiota of the offspring and its relevance to autism spectrum disorders. In this study, we established maternal pregnancy and lactation VD-deficient mouse models, employed shotgun macrogenomic sequencing to unveil alterations in the gut microbiome of offspring mice, and observed autism-related behaviours. Furthermore, fecal microbial transplantation (FMT) reversed repetitive and anxious behaviours and alleviated social deficits in offspring mice by modulating the gut microbiota and increasing short-chain fatty acid levels in the cecum, along with influencing the concentrations of claudin-1 and occludin in the colon. Our findings confirm that VDD during pregnancy and lactation is a risk factor for autism in the offspring, with disturbances in the structure and function of the offspring's gut microbiota contributing at least part of the effect. The study emphasises the importance of nutrition and gut health early in life. Simultaneously, this study further demonstrates the effect of VDD on ASD and provides potential ideas for early prevention and intervention of ASD.

Control list of high-priority chemicals based on 5-HT-RI functionality and the human health interference effects selective CNN-GRU deep learning model

The antidepressant drug known as 5-HT reuptake inhibitor (5-HT-RI) was commonly detected in biological tissues and result in significant adverse health effects. Homology modeling was used to characterize the functionalities (efficacy and resistance), and the adverse outcome pathway was used to characterize its human health interferences (olfactory toxicity, neurotoxicity, and gut microbial interference). The convolutional neural network coupled with the gated recurrent unit (CNN-GRU) deep learning method was used to construct a comprehensive model of 5-HT-RI functionality and human health interference effects selectivity with small sample data. The architecture with 2 SE, 320 neuronal nodes and 6-folds cross-validation showed the best applicability. The results showed that the confidence interval of the constructed model reached 90 % indicating that the model had reliable prediction ability and generalization ability. Based on the CNN-GRU deep learning model, seven high-priority chemicals with a weak comprehensive effect, including D-VEN, (1R,4S)-SER, S-FLX, CTP, S-CTP, NEF, and VEN, were screened. Based on the molecular three-dimensional structure information, a comprehensive-effect three-dimensional quantitative structure-activity relationship (3D-QSAR) model was constructed to confirm the reliability of the constructed control list of 5-HT-RI high-priority chemicals. Analysis with the ranking of calculated values based on the molecular dynamics method and predicted values based on the CNN-GRU deep learning model, we found that the consistency of the three methods was above 85 %. Additionally, by analyzing the sensitivity, molecular electrostatic potential, polar surface area of the comprehensive-effect CNN-GRU deep learning model, and the electrostatic field of the 3D-QSAR models, we found that the significant effects of five key characteristics (DM, Qyy, Qxz, I, and BP), molecular electronegativity, and polarity significantly affected the high-priority degree of 5-HT-RI. In this study, we provided reasonable and reliable prediction tools and discussed theoretical methods for the risk assessment of functionality and human health interference of emerging pollutants such as 5-HT-RI.

Mice prenatally exposed to valproic acid do not show autism-related disorders when fed with polyunsaturated fatty acid-enriched diets

Dietary supplementations with n-3 polyunsaturated fatty acid (PUFA) have been explored in autism spectrum disorder (ASD) but their efficiency and potential in ameliorating cardinal symptoms of the disease remain elusive. Here, we compared a n-3 long-chain (LC) PUFA dietary supplementation (n-3 supp) obtained from fatty fish with a n-3 PUFA precursor diet (n-3 bal) obtained from plant oils in the valproic acid (VPA, 450 mg/kg at E12.5) ASD mouse model starting from embryonic life, throughout lactation and until adulthood. Maternal and offspring behaviors were investigated as well as several VPA-induced ASD biological features: cerebellar Purkinje cell (PC) number, inflammatory markers, gut microbiota, and peripheral and brain PUFA composition. Developmental milestones were delayed in the n-3 supp group compared to the n-3 bal group in both sexes. Whatever the diet, VPA-exposed offspring did not show ASD characteristic alterations in social behavior, stereotypies, PC number, or gut microbiota dysbiosis while global activity, gait, peripheral and brain PUFA levels as well as cerebellar TNF-alpha levels were differentially altered by diet and treatment according to sex. The current study provides evidence of beneficial effects of n-3 PUFA based diets, including one without LCPUFAs, on preventing several behavioral and cellular symptoms related to ASD.

Amelioration of cognition impairments in the valproic acid-induced animal model of autism by ciproxifan, a histamine H3-receptor antagonist

Autism spectrum disorder is a neurodevelopmental disorder characterized by deficits in social communication and repetitive behavior. Many studies show that the number of cognitive impairmentscan be reduced by antagonists of the histamine H3 receptor (H3R). In this study, the effects of ciproxifan (CPX) (1 and 3 mg/kg, intraperitoneally) on cognitive impairments in rat pups exposed to valproic acid (VPA) (600 mg/kg, intraperitoneally) wereexamined on postnatal day 48-50 (PND 48-50) using marble-burying task (MBT), open field, novel object recognition (NOR), and Passive avoidance tasks. Famotidine (FAM) (10, 20, and 40 mg/kg, intraperitoneally) was also used to determine whether histaminergic neurotransmission exerts its procognitive effects via H2 receptors (H2Rs). Furthermore, a histological investigation was conducted to assess the degree of degeneration of hippocampal neurons. The results revealed that repetitive behaviors increased in VPA-exposed rat offspring in the MBT. In addition, VPA-exposed rat offspring exhibited more anxiety-like behaviors in the open field than saline-treated rats. It was found that VPA-exposed rat offspring showed memory deficits in NOR and Passive avoidance tasks. Our results indicated that 3 mg/kg CPX improved cognitive impairments induced by VPA, while 20 mg/kg FAM attenuated them. We concluded that 3 mg/kg CPX improved VPA-induced cognitive impairments through H3Rs. The histological assessment showed that the number of CA1 neurons decreased in the VPA-exposed rat offspring compared to the saline-exposed rat offspring, but this decrease was not significant. The histological assessment also revealed no significant differences in CA1 neurons in VPA-exposed rat offspring compared to saline-exposed rat offspring. However, CPX3 increased the number of CA1 neurons in the VPA + CPX3 group compared to the VPA + Saline group, but this increase was not significant. This study showed that rats prenatally exposed to VPA exhibit cognitive impairments in the MBT, open field, NOR, and Passive avoidance tests, which are ameliorated by CPX treatment on PND 48-50. In addition, morphological investigations showed that VPA treatment did not lead to neuronal degeneration in the CA1 subfield of the hippocampus in rat pups.

Testing the extreme male hypothesis in the valproate mouse model; sex-specific effects on plasma testosterone levels and tyrosine hydroxylase expression in the anteroventral periventricular nucleus, but not on parental behavior

Introduction

Autism is a neurodevelopmental disorder with a strong male bias in prevalence and severity. The extreme male hypothesis proposed that autism is a manifestation of extreme male traits as evidenced by increased masculine behaviors, hypermasculinization of some brain regions, and alterations in androgen metabolism. In the present study, the extreme male hypothesis was tested in the valproate (VPA) mouse model.

Methods

Females of the C57BL/6JOlaHsd mouse strain were treated with 500 mg/kg VPA on gestational day 12. Offspring of both sexes were tested at 3 to 4 months of age in the elevated plus maze (EPM), open field, sociability tests, and for parental behavior. After sacrifice at 5 to 6 months of age, plasma testosterone was measured in males, while the brains of both sexes were examined for tyrosine hydroxylase (TH) expression in the anteroventral periventricular nucleus (AVPV).

Results

VPA treatment significantly increased plasma testosterone levels and decreased AVPV TH expression in males, whereas the expression of TH in females remained at the same level. In parental behavior test none of the pup-oriented behavior was affected by VPA treatment in both sexes, the exception was nest quality which was lower after VPA exposure in males, but not in females.

Discussion

Our results suggest a hypermasculinizing effect of VPA that occurred specifically in males but not in females, and this effect could be related to changes in androgen physiology. Nevertheless, a generalized interpretation of the extreme male hypothesis on brain and behavior should be avoided due to the complex effects of VPA.

Canagliflozin alleviates valproic acid-induced autism in rat pups: Role of PTEN/PDK/PPAR-γ signaling pathways

Autism is complex and multifactorial, and is one of the fastest growing neurodevelopmental disorders. Canagliflozin (Cana) is an antidiabetic drug that exhibits neuroprotective properties in various neurodegenerative syndromes. This study investigated the possible protective effect of Cana against the valproic acid (VPA)-induced model of autism. VPA was injected subcutaneously (SC) into rat pups at a dose of 300 mg/kg, twice daily on postnatal day-2 (PD-2) and PD-3, and once on PD-4 to induce an autism-like syndrome. Graded doses of Cana were administered (5 mg/kg, 7.5 mg/kg, and 10 mg/kg, P.O.) starting from the first day of VPA injections and continued for 21 days. At the end of the experiment, behavioral tests and histopathological alterations were assessed. In addition, the gene expression of peroxisome proliferator-activated receptor γ (PPAR γ), lactate dehydrogenase A (LDHA), pyruvate dehydrogenase kinase (PDK), cellular myeloctomatosis (c-Myc) with protein expression of glucose transporter-1 (GLUT-1), phosphatase and tensin homolog (PTEN), and level of acetylcholine (ACh) were determined. Treatment with Cana significantly counteracted histopathological changes in the cerebellum tissues of the brain induced by VPA. Cana (5 mg/kg, 7.5 mg/kg, and 10 mg/kg) improved sociability and social preference, enhanced stereotypic behaviors, and decreased hyperlocomotion activity, in addition to its significant effect on the canonical Wnt/β-catenin pathway via the downregulation of gene expression of LDHA (22%, 64%, and 73% in cerebellum tissues with 51%, 60%, and 75% in cerebrum tissues), PDK (27%, 50%, and 67% in cerebellum tissues with 34%, 66%, and 77% in cerebrum tissues), c-Myc (35%, 44%, and 72% in cerebellum tissues with 19%, 58%, and 79% in cerebrum tissues), protein expression of GLUT-1 (32%, 48%, and 49% in cerebellum tissues with 30%, 50%, and 54% in cerebrum tissues), and elevating gene expression of PPAR-γ (2, 3, and 4 folds in cerebellum tissues with 1.5, 3, and 9 folds in cerebrum tissues), protein expression of PTEN (2, 5, and 6 folds in cerebellum tissues with 6, 6, and 10 folds in cerebrum tissues), and increasing the ACh levels (4, 5, and 7 folds) in brain tissues. The current study confirmed the ameliorating effect of Cana against neurochemical and behavioral alterations in the VPA-induced model of autism in rats.

The Role of Zinc and NMDA Receptors in Autism Spectrum Disorders

NMDA-type glutamate receptors are critical for synaptic plasticity in the central nervous system. Their unique properties and age-dependent arrangement of subunit types underpin their role as a coincidence detector of pre- and postsynaptic activity during brain development and maturation. NMDAR function is highly modulated by zinc, which is co-released with glutamate and concentrates in postsynaptic spines. Both NMDARs and zinc have been strongly linked to autism spectrum disorders (ASDs), suggesting that NMDARs are an important player in the beneficial effects observed with zinc in both animal models and children with ASDs. Significant evidence is emerging that these beneficial effects occur via zinc-dependent regulation of SHANK proteins, which form the backbone of the postsynaptic density. For example, dietary zinc supplementation enhances SHANK2 or SHANK3 synaptic recruitment and rescues NMDAR deficits and hypofunction in Shank3^ex13-16-/- and Tbr1^+/- ASD mice. Across multiple studies, synaptic changes occur in parallel with a reversal of ASD-associated behaviours, highlighting the zinc-dependent regulation of NMDARs and glutamatergic synapses as therapeutic targets for severe forms of ASDs, either pre- or postnatally. The data from rodent models set a strong foundation for future translational studies in human cells and people affected by ASDs.

Photobiomodulation Attenuated Cognitive Dysfunction and Neuroinflammation in a Prenatal Valproic Acid-Induced Autism Spectrum Disorder Mouse Model

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by social communication and interaction disorders, as well as repetitive and restrictive behaviors. To date, no effective treatment strategies have been identified. However, photobiomodulation (PBM) is emerging as a promising treatment for neurological and neuropsychiatric disorders. We used mice exposed to valproic acid (VPA) as a model of ASD and found that pathological behavioral and histological changes that may have been induced by VPA were attenuated by PBM treatment. Pregnant mice that had been exposed to VPA were treated with PBM three times. Thereafter, we evaluated the offspring for developmental disorders, motor function, hyperactivity, repetitive behaviors, and cognitive impairment. PBM attenuated many of the pathological behaviors observed in the VPA-induced ASD mouse model. In addition, pathophysiological analyses confirmed that the increase in activated microglia and astrocytes observed in the VPA-induced ASD mouse model was attenuated by PBM treatment. This suggests that PBM can counteract the behavioral changes caused by neuroinflammation in ASD. Therefore, our data show that PBM has therapeutic potential and may reduce the prevalence of neurodevelopmental disorders such as ASD.

Donepezil Beyond Alzheimer's Disease? A Narrative Review of Therapeutic Potentials of Donepezil in Different Diseases

Donepezil hydrochloride is an acetylcholine esterase inhibitor studied and approved to treat Alzheimer's disease (AD). However, this drug can have positive therapeutic potential in treating different conditions, including various neurodegenerative disorders such as other types of dementia, multiple sclerosis, Parkinson's disease, psychiatric and mood disorders, and even infectious diseases. Hence, this study reviewed the therapeutic potential of this drug in treating Alzheimer's and other diseases by reviewing the articles from databases including Web of Science, Scopus, PubMed, Cochrane, and Science Direct. It was shown that donepezil could affect the pathophysiology of these diseases via mechanisms such as increasing the concentration of acetylcholine, modulating local and systemic inflammatory processes, affecting acetylcholine receptors like nicotinic and muscarinic receptors, and activating various cellular signaling via receptors like sigma-1 receptors. Despite many therapeutic potentials, this drug has not yet been approved for treating non-Alzheimer's diseases, and more comprehensive studies are needed.

Combined Exposure to Chronic Sleep Deprivation and Caffeine Potentiates Behavioural Deficits by Altering Neurochemical Profile and Synaptophysin Expression in Long-Evans Rats

Using the Unpredictable Chronic Sleep Deprivation (UCSD) paradigm we developed, the combined effects of chronic sleep deprivation and high caffeine intake on prefrontal cortical synaptophysin expression, neurochemical profiles, and behavioural outcomes in Long-Evans rats were evaluated. The combination of chronic sleep deprivation and high-dose caffeine treatment produced varying degrees of behavioural impairments, depletion of antioxidants, serotonin, and an upregulation of acetylcholinesterase (AChE) activity in the prefrontal cortex. An immunohistochemical assessment revealed a reduction in synaptophysin protein expression in the prefrontal cortex following exposure to high-dose caffeine and chronic sleep deprivation. Overall, our findings support the advocacy for adequate sleep for optimal mental performance as a high intake of caffeine to attenuate the effects of sleep deprivation that may alter the neurochemical profile and synaptic plasticity in the prefrontal cortex, significantly increasing the risk of neuropsychiatric/degenerative disorders.

The Effects of Positive Allosteric Modulators of α7–nAChR on Social Play Behavior in Adolescent Rats Prenatally Exposed to Valproic Acid

There is still no effective treatment that addresses the core symptoms of autism spectrum disorders (ASD), including social and communication deficits. A comprehensive body of evidence points to the cholinergic system, including alpha7–nicotinic acetylcholine receptors (α7–nAChRs), as a potential target of pharmacotherapy. A promising approach is based on positive allosteric modulators (PAMs) of these receptors due to their advantages over direct agonists. Nevertheless, α7 n–AChR ligands have not been widely studied in the context of autism. Therefore, using one of the most widely used rodent models of ASD, that is, prenatal exposure to valproic acid (VPA), we examined the impact of α7–nAChR PAMs (PNU–120596 and CCMI) on socio-communicative behavior during social play in adolescent male and female rats. The current study demonstrated that PAM treatment affected certain aspects of socio-communicative behavior in adolescent rats. Accordingly, PNU–120596 ameliorated deficient play abilities in VPA-exposed males, as revealed by increased play time during a social encounter. In addition, this compound enhanced the emission of ultrasonic vocalizations that accompanied playful interactions. Moreover, we observed the overall effect of PNU–120596 on non-playful forms of social behavior (i.e., social exploration) and acoustic parameters (i.e., the duration) of emitted calls. The present results suggest the ability of α7–nAChR PAMs to facilitate socio-communicative behavior in adolescent rats.

Granulocyte Colony-Stimulating Factor Improved Core Symptoms of Autism Spectrum Disorder via Modulating Glutamatergic Receptors in the Prefrontal Cortex and Hippocampus of Rat Brains

Chronic neuroinflammation-induced anomalous glutamate receptor activation has been identified as one of the important factors in the pathogenesis of autism spectrum disorder (ASD). Thus, the current study was designed to elucidate the neuroprotective effect of the granulocyte colony-stimulating factor (G-CSF), a haemopoietic growth factor, an anti-inflammatory, and a neuroprotectant to decipher the underlying mechanism(s) in the valproic acid (VPA)-induced experimental model of ASD. Experimentally, the ASD rat model was induced by a single dose of VPA (600 mg/kg; i.p.) on gestation day 12.5 to the pregnant female rats. After birth, pups were treated with vehicle, normal saline 0.9% i.p., risperidone (2.5 mg/kg; i.p.), and G-CSF (10, 35, and 70 μg/kg; i.p.) from postnatal day (PND) 23 to 43. All the groups were subjected to various developmental and behavior tests from birth. The rats were sacrificed on PND 55, and their brain was excised and processed for biochemical parameters (oxidative stress, inflammatory markers, BDNF), histological examination (H&E, Nissl staining), NMDA, and AMPA receptor expression by immunohistochemistry, western blot, and real-time polymerase chain reaction evaluation. Also, the possible interaction of the G-CSF with NMDA and AMPA receptors was evaluated using the in-silico method. The results of the study showed that in VPA-exposed rats, postnatal treatment of G-CSF rescued all the behavioral abnormalities, oxidative stress, and inflammatory parameters in a dose-dependent manner while risperidone did not show any significant results. The in-silico analysis showed the direct interaction of G-CSF with NMDA and AMPA receptors. The upregulated expression of NMDA and AMPA both in the prefrontal cortex as well as hippocampus was alleviated by G-CSF thereby validating its anti-inflammatory and excitoprotective properties. Thus, G-CSF demonstrated neuroprotection against the core symptoms of autism in the VPA-induced rodent model, making it a potential candidate for the treatment of ASD.

Experimental Studies Indicate That ST-2223, the Antagonist of Histamine H3 and Dopamine D2/D3 Receptors, Restores Social Deficits and Neurotransmission Dysregulation in Mouse Model of Autism

Altered regulation of neurotransmitters may lead to many pathophysiological changes in brain disorders including autism spectrum disorder (ASD). Given the fact that there are no FDA-approved effective treatments for the social deficits in ASD, the present study determined the effects of chronic systemic treatment of the novel multiple-active H3R/D2R/D3R receptor antagonist ST-2223 on ASD-related social deficits in a male Black and Tan Brachyury (BTBR) mice. ST-2223 (2.5, 5, and 10 mg/kg, i.p.) significantly and dose-dependently mitigated social deficits and disturbed anxiety levels of BTBR mice (p < 0.05) in comparison to the effects of aripiprazole (1 mg/kg, i.p.). Moreover, levels of monoaminergic neurotransmitters quantified by LC-MS/MS in four brain regions including the prefrontal cortex, cerebellum, striatum, and hippocampus unveiled significant elevation of histamine (HA) in the cerebellum and striatum; dopamine (DA) in the prefrontal cortex and striatum; as well as acetylcholine (ACh) in the prefrontal cortex, striatum, and hippocampus following ST-2223 (5 mg/kg) administration (all p < 0.05). These in vivo findings demonstrate the mitigating effects of a multiple-active H3R/D2R/D3R antagonist on social deficits of assessed BTBR mice, signifying its pharmacological potential to rescue core ASD-related behaviors and altered monoaminergic neurotransmitters. Further studies on neurochemical alterations in ASD are crucial to elucidate the early neurodevelopmental variations behind the core symptoms and heterogeneity of ASD, leading to new approaches for the future therapeutic management of ASD.

Reinforced behavioral variability in the valproate rat model of autism spectrum disorder

Individuals diagnosed with autism spectrum disorder (ASD) tend to display restricted, repetitive behaviors and deficits in social interaction. Rats exposed to valproate (VPA) in utero have been shown to model symptoms of ASD. In previous research, VPA rats engaged in less social interaction and more repetitive responding than controls. The purpose of the present study was to further investigate behavioral variability in the VPA rat model of ASD by testing VPA and control rats in a reinforced-behavioral-variability operant task. In this procedure, rats emitted sequences of lever presses, some of which produced food. During baseline, food was delivered probabilistically, and variability was not required. Next, rats were exposed either to a variability contingency, in which food was only delivered following sequences that differed sufficiently from previous sequences (i.e., variability required), or to a yoked contingency, in which variability was not required. We hypothesized that VPA rats would behave less variably than controls in this task. However, VPA and control rats responded similarly variably when variability was required. Furthermore, VPA rats behaved slightly more variably than controls during baseline and yoked conditions, when variability was not required. These findings contribute to the complex literature surrounding the VPA rat model of ASD.

iTRAQ-Based Proteomics Analysis of Rat Cerebral Cortex Exposed to Valproic Acid before Delivery

Autism spectrum disorder (ASD) is a neurological and developmental disorder characterized by social and communication difficulties. Valproic acid (VPA) injection during pregnancy elicits autism-like behavior in the offspring, making it a classic animal model of ASD. However, the mechanisms involved have not yet been determined. In this study, we used iTRAQ (isobaric tags for relative and absolute quantification) proteomics analysis of the cerebral cortex of a VPA rat model (VPA group) and controls (CON group). The results showed that 79 differentially expressed proteins (DEPs) were identified between the VPA group and the CON group. Based on bioinformatics analysis, the DEPs were mainly enriched at synapses, especially glutamatergic synapses and GABAergic synapses. Some DEPs were involved in energy metabolism, thyroid hormone synthesis pathway, and Na⁺-K⁺-ATPase. Cytoskeleton and endoplasmic reticulum (ER) stress-related proteins were also involved. Some DEPs matched either the ASD gene database or previous reports on cerebral cortical transcriptome studies in VPA rat models. Dysregulation of these DEPs in the cerebral cortex of VPA rats may be responsible for autism-like behavior in rats. We also found that some DEPs were associated with neuropsychiatric disorders, implying that these diseases share common signaling pathways and mechanisms. Moreover, increased expression of DEPs was associated with energy metabolism in the cerebral cortex of VPA rats, implying that ASD may be a distinct type of mitochondrial dysfunction that requires further investigation.

Behavioral Deficits in Adolescent Mice after Sub-Chronic Administration of NMDA during Early Stage of Postnatal Development

Neurodevelopmental disorders are complex conditions that pose difficulty in the modulation of proper motor, sensory and cognitive function due to dysregulated neuronal development. Previous studies have reported that an imbalance in the excitation/ inhibition (E/I) in the brain regulated by glutamatergic and/or GABAergic neurotransmission can cause neurodevelopmental and neuropsychiatric behavioral deficits such as autism spectrum disorder (ASD). NMDA acts as an agonist at the NMDA receptor and imitates the action of the glutamate on that receptor. NMDA however, unlike glutamate, only binds to and regulates the NMDA receptor subtypes and not the other glutamate receptors. This study seeks to determine whether NMDA administration in mice i.e., over-activation of the NMDA system would result in long-lasting behavioral deficits in the adolescent mice. Both gender mice were treated with NMDA or saline at early postnatal developmental period with significant synaptogenesis and synaptic maturation. On postnatal day 28, various behavioral experiments were conducted to assess and identify behavioral characteristics. NMDAtreated mice show social deficits, and repetitive behavior in both gender mice at adolescent periods. However, only the male mice but not female mice showed increased locomotor activity. This study implies that neonatal exposure to NMDA may illicit behavioral features similar to ASD. This study also confirms the validity of the E/I imbalance theory of ASD and that NMDA injection can be used as a pharmacologic model for ASD. Future studies may explore the mechanism behind the gender difference in locomotor activity as well as the human relevance and therapeutic significance of the present findings.

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.

Duloxetine ameliorates valproic acid-induced hyperactivity, anxiety-like behavior, and social interaction deficits in zebrafish

Syndromic autism spectrum disorders (ASDs) are characterized by impaired social communication and repetitive/stereotyped behaviors. Currently available therapeutic agents against ASD have limited efficacy. Thus, searching for novel and effective drugs ameliorating core symptoms, in particular social deficits, is of utmost importance. Duloxetine (DLX), an antidepressant that has been identified as an agonist mimetic for the cell adhesion molecule L1, exhibits beneficial functions in vitro and in vivo. Therefore, in this study, we focused on the rapid and persistent neuroprotective function of DLX following valproic acid (VPA)-triggered hyperactivity, anxiety-like behavior and social deficits in zebrafish. Embryonic exposure to VPA reduced survival in a dose- and time-dependent manner, delayed hatching, and also resulted in a significant number of malformed larvae. After initial dose-response experiments in zebrafish larvae, 10 μM VPA exposure between 0.33 and 4.5 days post fertilization (dpf) was identified as an effective concentration that led to an early and persistent ASD-like phenotype in zebrafish. ASD-like elevated acetylcholine esterase (AChE) activity and reduced Akt-mTOR signaling was observed in zebrafish whole brain. Acute administration of DLX (4.5-6 dpf) reduced the VPA-induced ASD-like phenotype in zebrafish larvae. Additionally, such early-life acute DLX treatment had long-term effects in ameliorating social impairments, hyperactivity, and anxiety-like behaviors through adulthood. This was accompanied by reduced AChE activity and by normalized Akt-mTOR signaling. Overall, DLX treatment showed a long-term therapeutic effect on autistic-like behaviors, and alteration of AChE activity and Akt-mTOR signaling were identified as crucial in the VPA-induced ASD zebrafish model.

Social Deficits and Repetitive Behaviors Are Improved by Early Postnatal Low-Dose VPA Intervention in a Novel shank3-Deficient Zebrafish Model

Mutations of the SHANK3 gene are found in some autism spectrum disorder (ASD) patients, and animal models harboring SHANK3 mutations exhibit a variety of ASD-like behaviors, presenting a unique opportunity to explore the underlying neuropathological mechanisms and potential pharmacological treatments. The histone deacetylase (HDAC) valproic acid (VPA) has demonstrated neuroprotective and neuroregenerative properties, suggesting possible therapeutic utility for ASD. Therefore, SHANK3-associated ASD-like symptoms present a convenient model to evaluate the potential benefits, therapeutic window, and optimal dose of VPA. We constructed a novel shank3-deficient (shank3ab^–/–) zebrafish model through CRISPR/Cas9 editing and conducted comprehensive morphological and neurobehavioral evaluations, including of core ASD-like behaviors, as well as molecular analyses of synaptic proteins expression levels. Furthermore, different VPA doses and treatment durations were examined for effects on ASD-like phenotypes. Compared to wild types (WTs), shank3ab^–/– zebrafish exhibited greater developmental mortality, more frequent abnormal tail bending, pervasive developmental delay, impaired social preference, repetitive swimming behaviors, and generally reduced locomotor activity. The expression levels of synaptic proteins were also dramatically reduced in shank3ab^–/– zebrafish. These ASD-like behaviors were attenuated by low-dose (5 μM) VPA administered from 4 to 8 days post-fertilization (dpf), and the effects persisted to adulthood. In addition, the observed underexpression of grm5, encoding glutamate metabotropic receptor 5, was significantly improved in VPA-treated shank3ab^–/– zebrafish. We report for the first time that low-dose VPA administered after neural tube closure has lasting beneficial effects on the social deficits and repetitive behavioral patterns in shank3-deficient ASD model zebrafish. These findings provide a promising strategy for ASD clinical drug development.

A Need for Consistency in Behavioral Phenotyping for ASD: Analysis of the Valproic Acid Model

Autism spectrum disorder (ASD) is a highly prevalent and impairing neurodevelopmental disorder that affects 1 : 54 persons. Over the last several decades, the reported incidence of ASD in the US has increased potentially due to increased awareness and improved diagnostic measurement. Although ASD prevalence is increasing, the etiology of ASD remains relatively unknown. To better understand the neurological basis of ASD, rodent models of ASD have been developed for research. Currently, there is not a standardized set of behavioral tests to quantify ASD-like behavior in rodents. The goal of this review is to present an overview of the methodologies used to analyze ASD-like behaviors in rodents, focusing on the valproic acid (VPA) model, and illustrate inconsistencies between different approaches. Despite that the in utero VPA rodent model for ASD is widely used and extensively characterized, behaviors vary substantially between different researchers. Moving forward, consistency in behavioral method analytics would benefit progress in evaluating interventions for all models of ASD and help to uncover unique qualities underlying mechanisms causing ASD signs and symptoms.

The Multi-Targeting Ligand ST-2223 with Histamine H3 Receptor and Dopamine D2/D3 Receptor Antagonist Properties Mitigates Autism-Like Repetitive Behaviors and Brain Oxidative Stress in Mice

Autism spectrum disorder (ASD) is a complex heterogeneous neurodevelopmental disorder characterized by social and communicative impairments, as well as repetitive and restricted behaviors (RRBs). With the limited effectiveness of current pharmacotherapies in treating repetitive behaviors, the present study determined the effects of acute systemic treatment of the novel multi-targeting ligand ST-2223, with incorporated histamine H₃ receptor (H₃R) and dopamine D₂/D₃ receptor affinity properties, on ASD-related RRBs in a male Black and Tan BRachyury (BTBR) mouse model of ASD. ST-2223 (2.5, 5, and 10 mg/kg, i.p.) significantly mitigated the increase in marble burying and self-grooming, and improved reduced spontaneous alternation in BTBR mice (all p < 0.05). Similarly, reference drugs memantine (MEM, 5 mg/kg, i.p.) and aripiprazole (ARP, 1 mg/kg, i.p.), reversed abnormally high levels of several RRBs in BTBR (p < 0.05). Moreover, ST-2223 palliated the disturbed anxiety levels observed in an open field test (all p < 0.05), but did not restore the hyperactivity parameters, whereas MEM failed to restore mouse anxiety and hyperactivity. In addition, ST-2223 (5 mg/kg, i.p.) mitigated oxidative stress status by decreasing the elevated levels of malondialdehyde (MDA), and increasing the levels of decreased glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) in different brain parts of treated BTBR mice (all p < 0.05). These preliminary in vivo findings demonstrate the ameliorative effects of ST-2223 on RRBs in a mouse model of ASD, suggesting its pharmacological prospective to rescue core ASD-related behaviors. Further confirmatory investigations on its effects on various brain neurotransmitters, e.g., dopamine and histamine, in different brain regions are still warranted to corroborate and expand these initial data.

A Novel and Reliable Rat Model of Autism

Background: Autism spectrum disorders (ASD) is a complex neurodevelopmental disorder that lacks an ideal animal model to recapitulate the disease state of ASD. Previous studies have reported that transplanting gut microbiota of ASD patients into pregnant mice is sufficient to promote the changes of autism-like behavior in offspring. This study aims to explore whether fecal microbiota transplantation (FMT) can be used as a new method to establish the ASD animal model. Methods: We transplanted the fecal sample extract of ASD children into pregnant rats (rFMT) repeatedly to establish an ASD rat model (oFMT) and compare it with the classical valproic acid (VPA) model (oVPA). Results: First, we reveal that oFMT shows hypoevolutism and typical behavioral characteristics of ASD, consistent with the previous study. Second, the gut microbiota of oFMT mainly consists of Firmicutes and Bacteroidetes, recapitulating the abnormal gut microbiota of ASD. In oFMT, the abundance of Lactobacillus and Collinsella increased (Lactobacillus: oFMT 60.16%, oVPA 64.13%, oCON 40.11%; Collinsella: oFMT 3.73%, oVPA 1.39%, oCON 1.28%), compared with oVPA, gut microbiota also showed high consistency. Third, the expression of 5-hydroxytryptamine (5-HT) in oFMT serum increased, γ-aminobutyric acid (GABA) and norepinephrine (NE) in oFMT serum decreased. Fourth, the gut microbiota of oFMT also has some ASD characteristic gut microbiota not found in oVPA. Fifth, pregnant rat with VPA showed significant immune activation, while those with FMT showed relatively minor immune activation. Limitations: Although the mechanism of establishing FMT autism rat model (oFMT) has not clearly defined, the data show that the model has high structural validity, and FMT model is likely to be a new and reliable potential animal model of ASD, and will have potential value in studying gut microbiota of ASD. Conclusions: The FMT autism rat model has high structural validity, and the FMT model is likely to be a new and reliable potential animal model of ASD.

Epigenetically Upregulated T-Type Calcium Channels Contribute to Abnormal Proliferation of Embryonic Neural Progenitor Cells Exposed to Valproic Acid

Valproic acid is a clinically used mood stabilizer and antiepileptic drug. Valproic acid has been suggested as a teratogen associated with the manifestation of neurodevelopmental disorders, such as fetal valproate syndrome and autism spectrum disorders, when taken during specific time window of pregnancy. Previous studies proposed that prenatal exposure to valproic acid induces abnormal proliferation and differentiation of neural progenitor cells, presumably by inhibiting histone deacetylase and releasing the condensed chromatin structure. Here, we found valproic acid up-regulates the transcription of T-type calcium channels by inhibiting histone deacetylase in neural progenitor cells. The pharmacological blockade of T-type calcium channels prevented the increased proliferation of neural progenitor cells induced by valproic acid. Differentiated neural cells from neural progenitor cells treated with valproic acid displayed increased levels of calcium influx in response to potassium chloride-induced depolarization. These results suggest that prenatal exposure to valproic acid up-regulates T-type calcium channels, which may contribute to increased proliferation of neural progenitor cells by inducing an abnormal calcium response and underlie the pathogenesis of neurodevelopmental disorders.

Simultaneous Blockade of Histamine H3 Receptors and Inhibition of Acetylcholine Esterase Alleviate Autistic-Like Behaviors in BTBR T+ tf/J Mouse Model of Autism

Autism spectrum disorder (ASD) is a heterogenous neurodevelopmental disorder defined by persistent deficits in social interaction and the presence of patterns of repetitive and restricted behaviors. The central neurotransmitters histamine (HA) and acetylcholine (ACh) play pleiotropic roles in physiological brain functions that include the maintenance of wakefulness, depression, schizophrenia, epilepsy, anxiety and narcolepsy, all of which are found to be comorbid with ASD. Therefore, the palliative effects of subchronic systemic treatment using the multiple-active test compound E100 with high H₃R antagonist affinity and AChE inhibitory effect on ASD-like behaviors in male BTBR T+tf/J (BTBR) mice as an idiopathic ASD model were assessed. E100 (5, 10 and 15 mg/kg, i.p.) dose-dependently palliated social deficits of BTBR mice and significantly alleviated the repetitive/compulsive behaviors of tested animals. Moreover, E100 modulated disturbed anxiety levels, but failed to modulate hyperactivity parameters, whereas the reference AChE inhibitor donepezil (DOZ, one milligram per kilogram) significantly obliterated the increased hyperactivity measures of tested mice. Furthermore, E100 mitigated the increased levels of AChE activity in BTBR mice with observed effects comparable to that of DOZ and significantly reduced the number of activated microglial cells compared to the saline-treated BTBR mice. In addition, the E100-provided effects on ASD-like parameters, AChE activity, and activated microglial cells were entirely reversed by co-administration of the H₃R agonist (R)-α-methylhistamine (RAM). These initial overall results observed in an idiopathic ASD mice model show that E100 (5 mg/kg) alleviated the assessed behavioral deficits and demonstrate that simultaneous targeting of brain histaminergic and cholinergic neurotransmissions is crucial for palliation of ASD-like features, albeit further in vivo assessments on its effects on brain levels of ACh as well as HA are still needed.

Prenatal pregabalin is associated with sex-dependent alterations in some behavioral parameters in valproic acid-induced autism in rat offspring

This study was performed to evaluate the effects of prenatal exposure to pregabalin (PGB) on behavioral changes of rat offspring in an animal model of valproic acid (VPA)-induced autism-like symptoms. Pregnant rats received VPA (600 mg/kg/i.p.) once at 12.5 gestational days for autism-like symptom induction in offspring. After the delivery single male and single female offspring from each mother were randomly selected for behavioral test (anxiety, pain response, pleasure, and motor function) at 60th day adulthood (n = 7). Offspring received prenatal PGB (15 & 30 mg/kg/i.p.) during gestational days 9.5 to 15.5 either alone or in combination with VPA (PGB15, PGB30, PGB15 + VPA, and PGB30 + VPA). Control offspring received normal saline during the same period. The result showed that prenatal VPA exposure was associated with autism-like behaviors in rat offspring. PGB treatment during the gestational period revealed significant reduction in sucrose preference test and anxiety in elevated plus maze and open field test in offspring. Also, PGB treatments exhibited a dose-dependent increase in pain threshold in prenatally VPA exposed rats in tail-flick and hot plate test. Also, there was a sex-related significant impairment in motor function in beam balance and open field test, and male rats were affected more than females. However, no significant sex differences in sucrose preference and pain sensitivity were observed in prenatal PGB-treated rat offspring. In conclusion, prenatal exposure to VPA increased the risk of autism-like behaviors in the offspring rats, and PGB treatment during the gestational period was associated with some beneficial effects, including anxiety reduction and motor impairment in autism-like symptoms in rat offspring.

The Dual-Active Histamine H3 Receptor Antagonist and Acetylcholine Esterase Inhibitor E100 Alleviates Autistic-Like Behaviors and Oxidative Stress in Valproic Acid Induced Autism in Mice

The histamine H3 receptor (H3R) functions as auto- and hetero-receptors, regulating the release of brain histamine (HA) and acetylcholine (ACh), respectively. The enzyme acetylcholine esterase (AChE) is involved in the metabolism of brain ACh. Both brain HA and ACh are implicated in several cognitive disorders like Alzheimer’s disease, schizophrenia, anxiety, and narcolepsy, all of which are comorbid with autistic spectrum disorder (ASD). Therefore, the novel dual-active ligand E100 with high H3R antagonist affinity (hH3R: K_i = 203 nM) and balanced AChE inhibitory effect (EeAChE: IC₅₀ = 2 µM and EqBuChE: IC₅₀ = 2 µM) was investigated on autistic-like sociability, repetitive/compulsive behaviour, anxiety, and oxidative stress in male C57BL/6 mice model of ASD induced by prenatal exposure to valproic acid (VPA, 500 mg/kg, intraperitoneal (i.p.)). Subchronic systemic administration with E100 (5, 10, and 15 mg/kg, i.p.) significantly and dose-dependently attenuated sociability deficits of autistic (VPA) mice in three-chamber behaviour (TCB) test (all p < 0.05). Moreover, E100 significantly improved repetitive and compulsive behaviors by reducing the increased percentage of marbles buried in marble-burying behaviour (MBB) (all p < 0.05). Furthermore, pre-treatment with E100 (10 and 15 mg/kg, i.p.) corrected decreased anxiety levels (p < 0.05), however, failed to restore hyperactivity observed in elevated plus maze (EPM) test. In addition, E100 (10 mg/kg, i.p.) mitigated oxidative stress status by increasing the levels of decreased glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT), and decreasing the elevated levels of malondialdehyde (MDA) in the cerebellar tissues (all p < 0.05). Additionally, E100 (10 mg/kg, i.p.) significantly reduced the elevated levels of AChE activity in VPA mice (p < 0.05). These results demonstrate the promising effects of E100 on in-vivo VPA-induced ASD-like features in mice, and provide evidence that a potent dual-active H3R antagonist and AChE inhibitor (AChEI) is a potential drug candidate for future therapeutic management of autistic-like behaviours.

Ethanol exposure during the brain growth spurt affects social behavior and increases susceptibility to acute ethanol effects during adolescence in male mice

The brain is particularly vulnerable to ethanol effects during its growth spurt. Outcomes of early ethanol exposure such as hyperactivity have been extensively investigated; however, persons with fetal alcohol spectrum disorder frequently have social impairments and are heavy drinkers. Despite that, scant information is available regarding the neurobiological basis of these latter behavioral issues. Here, Swiss mice exposed to ethanol (Etoh, 5 g/kg i.p., alternate days) or saline during the brain growth spurt [postnatal day (PN) 2 to 8] were used to assess social behavior after an ethanol challenging during adolescence. At PN39, animals were administered with a single ethanol dose (1 g/Kg) or water by gavage and were then evaluated in the three-chamber sociability test. We also evaluated corticosterone serum levels and the frontal cerebral cortex serotoninergic system. Etoh males showed reductions in sociability. Ethanol challenging reverted these alterations in social behavior, reduced corticosterone levels, and increased the 5-HT₂ receptor binding of male Etoh mice. No alterations were observed in 5-HT and 5-HIAA contents. These data support the idea that ethanol exposure during the brain growth spurt impacts social abilities during adolescence, alters ethanol reexposure effects, and suggests that stress response and serotoninergic system play roles in this phenomenon.

Adenylate cyclase activator forskolin alleviates intracerebroventricular propionic acid-induced mitochondrial dysfunction of autistic rats

Neuronal mitochondrial dysfunction increases inflammatory mediators and leads to free radical generation and anti-oxidant enzymatic alterations, which are major neuropathological hallmarks responsible for autism. Mitochondrial dysfunction in autism is associated with decreased ATP levels due to reduced levels of cyclic adenosine monophosphate. Rat models of autism were established by intracerebroventricular injection of propionic acid. These rat models had memory dysfunction, decreased muscle coordination and gait imbalance. Biochemical estimation of propionic acid-treated rats showed changes in enzyme activity in neuronal mitochondrial electron transport chain complexes and increases in pro-inflammatory cytokines, oxidative stress and lipid biomarkers. Oral administration of 10, 20 and 30 mg/kg adenylate cyclase activator forskolin for 15 days reversed these changes in a dose-dependent manner. These findings suggest that forskolin can alleviate neuronal mitochondrial dysfunction and improve neurological symptoms of rats with autism. This study was approved by the RITS/IAEC, SIRSA, HARYANA on March 3, 2014 (approval No. RITS/IAEC/2014/03/03).

Recapitulation of Neuropsychiatric Behavioral Features in Mice Using Acute Low-dose MK-801 Administration

Despite some innate limitations, animal models are a potent investigative tool when used to model specific symptoms of a disorder. For example, MK-801, an N-methyl-D-aspartate receptor antagonist, is used as a pharmacological tool to induce symptoms found in some neuropsychiatric disorders. However, a close examination of literature suggests that the application window of MK-801 doses is relatively narrow between individual behavioral paradigms, necessitating careful characterization of the evoked behavioral aberrations and the doses used to induce them. Moreover, variation in behaviors depending on the animal strain, gender of the subject, and the timing of administration is observed, making it difficult to compare the behavioral characteristics reported in different studies. We aim to characterize the behavioral aberrations induced by different doses of MK-801 in CD-1 mice and create a ready reference for future studies. We used CD-1 mice to recapitulate behavioral impairments resulting from acute administration of MK-801. In 0.1 mg kg⁻¹, we observed diminished spontaneous alteration during the Y-maze test, while 0.12 mg kg⁻¹ resulted in hyperlocomotion and social deficit. Mice treated with 0.2 and 0.3 mg kg⁻¹ of MK-801 demonstrated a decreased self-grooming. Finally, all doses significantly impaired cliff avoidance behaviors suggesting increased impulsivity. These results affirm that MK-801 can effectively model various symptoms of different neuropsychiatric disorders in a dose-dependent manner. The observed sensitivity against spatial-memory impairment and impulsive behaviors at low concentration of MK-801 suggest that MK801 may modulate cognitive function and impulsivity in even lower concentration before it can modulate other behavioral domains.

Neuroprotective potential of solanesol in intracerebroventricular propionic acid induced experimental model of autism: Insights from behavioral and biochemical evidence

Autism is the category used within the newest edition of the diagnostic and statistical manual of neurodevelopmental disorders. Autism is a spectrum of disorder where a variety of behavioural patterns observed in autistic patients, such as stereotypes and repetitive behavior, hyperexcitability, depression-like symptoms, and memory and cognitive dysfunctions. Neuropathological hallmarks that associated with autism are mitochondrial dysfunction, oxidative stress, neuroinflammation, Neuro-excitation, abnormal synapse formation, overexpression of glial cells in specific brain regions like cerebellum, cerebral cortex, amygdala, and hippocampus. ICV injection of propionic acid (PPA) (4 μl/0.26 M) mimics autistic-like behavioral and biochemical alterations in rats. Literature findings reveal that there is a link between autism neuronal mitochondrial coenzyme-Q10 (CoQ10) and ETC-complexes dysfunctions are the keys pathogenic events for autism. Therefore, in the current study, we explore the neuroprotective interventions of Solanesol (SNL) 40 and 60 mg/kg alone and in combination with standard drugs Aripiprazole (ARP) 5 mg/kg, Citalopram (CTP) 10 mg/kg, Memantine (MEM) 5 mg/kg and Donepezil (DNP) 3 mg/kg to overcome behavioral and biochemical alterations in PPA induced experimental model of Autism. Chronic treatment with SNL 60 mg/kg in combination with standard drug shows a marked improvement in locomotion, muscle coordination, long-term memory and the decrease in depressive behavior. While, chronic treatment of SNL alone and in combination with standard drug aripiprazole, citalopram, donepezil, and memantine shows the Neuroprotective potential by enhancing the cognitive deficits, biochemical alterations along with reducing the level of inflammatory mediators and oxidative stress.

Gene-environment interaction counterbalances social impairment in mouse models of autism

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social communication deficits and repetitive/restricted behaviors. Although gene-environment interactions may explain the heterogeneous etiology of ASD, it is still largely unknown how the gene-environment interaction affects behavioral symptoms and pathophysiology in ASD. To address these questions, we used Cntnap2 knockout mice (genetic factor, G) exposed to valproic acid during embryonic development (environmental factor, E) as a gene-environment interaction (G × E) model. Paradoxically, the social deficits observed in the respective G and E models were improved in the G × E model; however, the high seizure susceptibility was more severe in the G × E -model than in the G and E models. Repetitive self-grooming and hyperactivity did not differ among the three models. The amplitudes of miniature excitatory postsynaptic currents in layer 2/3 pyramidal neurons of the medial prefrontal cortex were aberrant and similar in the G × E model when compared to the control group. Our findings suggest that the interaction of two risk factors does not always aggravate ASD symptoms but can also alleviate them, which may be key to understanding individual differences in behavioral phenotypes and symptom intensity.

Prevention or Amelioration of Autism-Like Symptoms in Animal Models: Will it Bring Us Closer to Treating Human ASD?

Since the first animal model of valproic acid (VPA) induced autistic-like behavior, many genetic and non-genetic experimental animal models for Autism Spectrum Disorder (ASD) have been described. The more common non-genetic animal models induce ASD in rats and mice by infection/inflammation or the prenatal or early postnatal administration of VPA. Through the establishment of these models, attempts have been made to ameliorate or even prevent ASD-like symptoms. Some of the genetic models have been successfully treated by genetic manipulations or the manipulation of neurotransmission. Different antioxidants have been used (i.e., astaxanthin, green tea, piperine) to reduce brain oxidative stress in VPA-induced ASD models. Agents affecting brain neurotransmitters (donepezil, agmatine, agomelatine, memantine, oxytocin) also successfully reduced ASD-like symptoms. However, complete prevention of the development of symptoms was achieved only rarely. In our recent study, we treated mouse offspring exposed on postnatal day four to VPA with S-adenosine methionine (SAM) for three days, and prevented ASD-like behavior, brain oxidative stress, and the changes in gene expression induced by VPA. In this review, we describe, in addition to our data, the existing literature on the prevention/amelioration of ASD-like symptoms. We also discuss the possible mechanisms underlying some of these phenomena. Finally, we describe some of the clinical trials in children with ASD that were carried out as a result of data from animal studies, especially those with polyunsaturated fatty acids (PUFAs).

Pharmacological modulation of AMPA receptor rescues social impairments in animal models of autism

Autism spectrum disorder (ASD) is a neurodevelopmental disorder, featuring social communication deficit and repetitive/restricted behaviors as common symptoms. Its prevalence has continuously increased, but, till now, there are no therapeutic approaches to relieve the core symptoms, particularly social deficit. In previous studies, abnormal function of the glutamatergic neural system has been proposed as a critical mediator and therapeutic target of ASD-associated symptoms. Here, we investigated the possible roles of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) in autism symptoms using two well-known autistic animal models, Cntnap2 knockout (KO) mice and in utero valproic acid-exposed ICR (VPA) mice. We found that Cntnap2 KO mice displayed decreased glutamate receptor expression and transmission. Contrarily, VPA mice exhibited increased glutamate receptor expression and transmission. Next, we investigated whether AMPAR modulators (positive-allosteric-modulator for Cntnap2 KO mice and antagonist for VPA mice) can improve autistic symptoms by normalizing the aberrant excitatory transmission in the respective animal models. Interestingly, the AMPAR modulation specifically ameliorated social deficits in both animal models. These results indicated that AMPAR-derived excitatory neural transmission changes can affect normal social behavior. To validate this, we injected an AMPAR agonist or antagonist in control ICR mice and, interestingly, these treatments impaired only the social behavior, without affecting the repetitive and hyperactive behaviors. Collectively, these results provide insight into the role of AMPARs in the underlying pathophysiological mechanisms of ASD, and demonstrate that modulation of AMPAR can be a potential target for the treatment of social behavior deficits associated with ASD.

Prenatal Neuropathologies in Autism Spectrum Disorder and Intellectual Disability: The Gestation of a Comprehensive Zebrafish Model

Autism spectrum disorder (ASD) and intellectual disability (ID) are neurodevelopmental disorders with overlapping diagnostic behaviors and risk factors. These include embryonic exposure to teratogens and mutations in genes that have important functions prenatally. Animal models, including rodents and zebrafish, have been essential in delineating mechanisms of neuropathology and identifying developmental critical periods, when those mechanisms are most sensitive to disruption. This review focuses on how the developmentally accessible zebrafish is contributing to our understanding of prenatal pathologies that set the stage for later ASD-ID behavioral deficits. We discuss the known factors that contribute prenatally to ASD-ID and the recent use of zebrafish to model deficits in brain morphogenesis and circuit development. We conclude by suggesting that a future challenge in zebrafish ASD-ID modeling will be to bridge prenatal anatomical and physiological pathologies to behavioral deficits later in life.

Molecular Pathology and Pharmacological Treatment of Autism Spectrum Disorder-Like Phenotypes Using Rodent Models

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder with a high prevalence rate. The core symptoms of ASD patients are impaired social communication and repetitive behavior. Genetic and environmental factors contribute to pathophysiology of ASD. Regarding environmental risk factors, it is known that valproic acid (VPA) exposure during pregnancy increases the chance of ASD among offspring. Over a decade of animal model studies have shown that maternal treatment with VPA in rodents recapitulates ASD-like pathophysiology at a molecular, cellular and behavioral level. Here, we review the prevailing theories of ASD pathogenesis, including excitatory/inhibitory imbalance, neurotransmitter dysfunction, dysfunction of mTOR and endocannabinoid signaling pathways, neuroinflammation and epigenetic alterations that have been associated with ASD. We also describe the evidence linking neuropathological changes to ASD-like behavioral abnormalities in maternal VPA-treated rodents. In addition to obtaining an understanding of the neuropathological mechanisms, the VPA-induced ASD-like animal models also serve as a good platform for testing pharmacological reagents that might be use treating ASD. We therefore have summarized the various pharmacological studies that have targeted the classical neurotransmitter systems, the endocannabinoids, the Wnt signal pathway and neuroinflammation. These approaches have been shown to often be able to ameliorate the ASD-like phenotypes induced by maternal VPA treatments.

Motor Impairments Correlate with Social Deficits and Restricted Neuronal Loss in an Environmental Model of Autism

Background

Motor impairments are amongst the earliest and most consistent signs of autism spectrum disorders but are not used as diagnostic criteria. In addition, the relationship between motor and cognitive impairments and their respective neural substrates remain unknown.

Methods

Here, we aimed at determining whether a well-acknowledged animal model of autism spectrum disorders, the valproic acid model, displays motor impairments and whether they may correlate with social deficits and neuronal loss within motor brain areas. For this, pregnant female mice (C57BL/6J) received valproic acid (450 mg/kg) at embryonic day 12.5 and offspring underwent a battery of behavioral analyses before being killed for histological correlates in motor cortex, nigrostriatal pathway, and cerebellum.

Results

We show that while valproic acid male mice show both social and motor impairments, female mice only show motor impairments. Prenatal valproic acid exposure induces specific cell loss within the motor cortex and cerebellum and that is of higher magnitude in males than in females. Finally, we demonstrate that motor dysfunction correlates with reduced social behavior and that motor and social deficits both correlate with a loss of Purkinje cells within the Crus I cerebellar area.

Conclusions

Our results suggest that motor dysfunction could contribute to social and communication deficits in autism spectrum disorders and that motor and social deficits may share common neuronal substrates in the cerebellum. A systematic assessment of motor function in autism spectrum disorders may potentially help the quantitative diagnosis of autism spectrum disorders and strategies aimed at improving motor behavior may provide a global therapeutic benefit.

The histamine H3R antagonist DL77 attenuates autistic behaviors in a prenatal valproic acid-induced mouse model of autism

Autistic spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairment in social communication and restricted/repetitive behavior patterns or interests. Antagonists targeting histamine H3 receptor (H3R) are considered potential therapeutic agents for the therapeutic management of different brain disorders, e.g., cognitive impairments. Therefore, the effects of subchronic treatment with the potent and selective H3R antagonist DL77 (5, 10, or 15 mg/kg, i.p.) on sociability, social novelty, anxiety, and aggressive/repetitive behavior in male Tuck-Ordinary (TO) mice with ASD-like behaviors induced by prenatal exposure to valproic acid (VPA, 500 mg/kg, i.p.) were evaluated using the three-chamber test (TCT), marble burying test (MBT), nestlet shredding test (NST), and elevated plus maze (EPM) test. The results showed that VPA-exposed mice exhibited significantly lower sociability and social novelty preference compared to VPA-exposed mice that were pretreated with DL77 (10 or 15 mg/kg, i.p.). VPA-exposed mice presented a significantly higher percentage of buried marbles in MBT and shredded nestlet significantly more in NST compared to the control groups. However, VPA-exposed animals pretreated with DL77 (10 or 15 mg/kg, i.p.) buried a reduced percentage of marbles in MBT and presented a significantly lower percentage of shredding behavior in NST. On the other hand, pretreatment with DL77 (5, 10, or 15 mg/kg, i.p.) failed to restore the disturbed anxiety levels and hyperactivity observed in VPA-exposed animals in EPM, whereas the reference drug donepezil (DOZ, 1 mg/kg, i.p.) significantly palliated the anxiety and reduced the hyperactivity measures of VPA-exposed mice. Furthermore, pretreatment with DL77 (10 or 15 mg/kg, i.p.) modulated oxidative stress status by increasing GSH and decreasing MDA, and it attenuated the proinflammatory cytokines IL-1β, IL-6 and TNF-α exacerbated by lipopolysaccharide (LPS) challenge, in VPA-exposed mouse brain tissue. Taken together, these results provide evidence that modulation of brain histaminergic neurotransmission, such as by subchronic administration of the H3R antagonist DL77, may serve as an effective pharmacological therapeutic target to rescue ASD-like behaviors in VPA-exposed animals, although further investigations are necessary to corroborate and expand these initial data.