An overview of modeling and behavioral assessment of autism in the rodent

Female mice prenatally exposed to valproic acid exhibit complex and prolonged social behavior deficits

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized mainly by deficits in social communication and stereotyped and restricted behavior and interests with a male to female bias of 4.2/1. Social behavior in ASD animal models is commonly analyzed in males, and seldomly in females, using the widely implemented three-chambers test procedure. Here, we implemented a novel procedure, the Live Mouse Tracker (LMT), combining artificial intelligence, machine learning procedures and behavioral measures. We used it on mice that were prenatally exposed to valproic acid (VPA) (450 mg/kg) at embryonic day 12.5, a widely recognized and potent ASD model that we had previously extensively characterized. We focused on female mice offspring, in which social deficits have been rarely documented when using the 3-CT procedure. We recorded several parameters related to social behavior in these mice, continuously for three days in groups of four female mice. Comparisons were made on groups of 4 female mice with the same treatment (4 saline or 4 VPA) or with different treatments (3 saline and 1 VPA). We report that VPA females show several types of social deficits, which are different in nature and magnitude in relation with time. When VPA mice were placed in the LMT alongside saline mice, their social deficits showed significant improvement as early as 1 h from the start of the experiment, lasting up to 3 days throughout the duration of the experiment. Our findings suggest that ASD may be underdiagnosed in females. They also imply that ASD-related social deficits can be ameliorated by the presence of typical individuals.

Possible role of NO/NMDA pathway in the autistic-like behaviors induced by maternal separation stress in mice

Autism spectrum disorder (ASD) is a complex neurodevelopmental disorder. Maternal separation (MS) stress is an established model of early-life stress associated with autistic-like behaviors. Altered glutamatergic and nitrergic neurotransmissions may contribute to the pathophysiology of ASD. However, the specific mechanisms underlying these alterations and their relationship to MS-induced autistic-like behaviors remain unclear. Addressing this knowledge gap, this study aims to elucidate the involvement of the nitric oxide (NO)/ N-methyl-D-aspartate (NMDA) pathway in MS-induced autistic-like behaviors in mice. This knowledge has the potential to guide future research, potentially leading to the development of targeted interventions or treatments aimed at modulating the NO/NMDA pathway to ameliorate ASD symptoms. Ninety male Naval Medical Research Institute (NMRI) mice were assigned to six groups (n = 15) comprising a control group (treated with saline) and five groups subjected to MS and treated with saline, ketamine, NMDA, L-NAME, and L-arginine. Behavioral tests were conducted, including the three-chamber test, shuttle box, elevated plus-maze, and marble burying test. Gene expression of iNOS, nNOS, and NMDA-R subunits (NR2A and NR2B), along with nitrite levels, was evaluated in the hippocampus. The findings demonstrated that MS induced autistic-like behaviors, accompanied by increased gene expression of iNOS, nNOS, NR2B, NR2A, and elevated nitrite levels in the hippocampus. Modulation of the NO/NMDA pathway with activators and inhibitors altered the effects of MS. These results suggest that the NO/NMDA pathway plays a role in mediating the negative effects of MS and potentially contributes to the development of autistic-like behaviors in maternally separated mice.

Effects of Nicotine Administration in an Enriched Environment on the Behavior of Male MK-801-Exposed Rats

Background

Smoking is more common in patients with schizophrenia than in healthy populations. Some controversial hypotheses connect the disease with the high prevalence of smoking. Moreover, environmental factors affect the severity of the positive and negative symptoms of schizophrenia. The current study aimed to assess the effect of enriched environment (EE) and nicotine on the MK-801 animal model of schizophrenia.

Methods

Male Wistar rat pups randomly received saline or MK-801 (dose:1 mg/kg) for five days from the sixth postnatal day (P) until the tenth. The pups were placed in EE or standard cages (SCs) after weaning (P21). Morris water maze (MWM) was used to assess spatial learning and memory. The rats received 0.6 mg/kg nicotine twice for three days at the end of the second month and were examined in an open-field box and three-chamber social interaction test.

Findings

MK-801 rats' behaviors were the same as those of the saline rats when they were exposed to nicotine. No positive effects of EE were observed when the animals were exposed to nicotine.

Conclusion

The results suggested that nicotine decreased schizophrenia-like symptoms and covered the positive effects of EE.

Audiogenic Seizures and Social Deficits: No Aggravation Found in Krushinsky-Molodkina Rats

Epilepsy or epileptic syndromes affect more than 70 million people, often comorbid with autism spectrum disorders (ASD). Seizures are concerned as a factor for social regression in ASD. A stepwise experimental approach to this problem requires an animal model to provoke seizures and monitor subsequent behavior. We used rats of the Krushinsky-Molodkina (KM) strain as a validated inbred genetic model for human temporal lobe epilepsy, with recently described social deficiency and hypolocomotion. Generalized tonic-clonic seizures in KM rats are sound-triggered, thus being controlled events in drug-naïve animals. We studied whether seizure experience would aggravate contact deficits in these animals. Locomotor and contact parameters were registered in "the elevated plus maze", "socially enriched open field", and "social novelty/social preference tests" before and after sound-provoked seizures. The triple seizure provocations minimally affected the contact behavior. The lack of social drive in KM rats was not accompanied by a submissive phenotype, as tested in "the tube dominance test", but featured with a poor contact repertoire. Here, we confirmed our previous findings on social deficits in KM rats. The contact deficiency was dissociated from hypolocomotion and anxiety and did not correlate with seizure experience. It was established that experience of rare, generalized tonic-clonic convulsions did not lead to an impending regress in contact motivation, as seen in an animal model of genetic epilepsy and comorbid social deficiency. One of the oldest animal models for epilepsy has a translational potential to study mechanisms of social behavioral deficits in future neurophysiological and pharmacological research.

Astrocyte responses to postnatal erythropoietin and nano-erythropoietin treatments in a valproic acid-induced animal model of autism

BACKGROUND

Despite ample evidence of the potential protective effects of erythropoietin (EPO) on the developing brain, no study has addressed the effects of postnatal EPO on behaviors and brain tissue of animal models of autism. In the present study, we examined the therapeutic effects of postnatal erythropoietin on stereotypic behaviors and astrocyte responses via glial fibrillary acidic protein (GFAP) and S100 calcium-binding protein B (S100B) immunohistochemistry in a valproic acid (VPA) animal model of autism. Also, we compared the effects of EPO with EPO-loaded solid lipid nanoparticles (NEPO) because the blood-brain barrier has limited permeability to EPO.

METHODS

Pregnant rats received a single dose of VPA (600mg/kg) at gestational day 12.5. EPO (2000U/kg) and EPO-loaded solid lipid nanoparticles (NEPO1000 and 2000U/kg) were injected intraperitoneally from postnatal days 1-5. Repetitive behaviors in male offspring were assessed by a marble burying test. The immune-staining method was performed to evaluate S100B and GFAP-positive cells in the prefrontal cortex and hippocampal CA1 region.

RESULTS

VPA animal models revealed more repetitive behavior and displayed higher astrogliosis in the prefrontal cortex (PFC) and hippocampus (CA1) regions. The repetitive behaviors were ameliorated relatively in VPA groups with NEPO2000 treatment, and astrogliosis was reduced even when VPA rats were treated with a lower dosage of NEPO.

CONCLUSION

Our results indicate beneficial effects of postnatal NEPO exposure in the VPA animal model of autism, which proposes it as an early treatment in infants with, or at risk of, autism.

The effects of postnatal erythropoietin and nano-erythropoietin on behavioral alterations by mediating K-Cl co-transporter 2 in the valproic acid-induced rat model of autism

In this study, based on the excitatory/inhibitory imbalance theory of autism, the time window of GABA switch, the role of K-Cl co-transporter 2 (KCC2) in adjustment GABA switch, and brain permeability to erythropoietin (EPO), the effects of postnatal -EPO and- nano- erythropoietin (NEPO) have been evaluated in the valproic acid (VPA) rat model of autism. The VPA was administered for animal modeling of autism at gestational day (GD) 12.5 (600 mg/kg). Male offsprings were injected with EPO and NEPO in a clinically proper postnatal dosing regimen on postnatal days (PND) 1-5, and autistic-like behaviors were tested at the end of the first month. Then animals were sacrificed, and neuron morphology and KCC2 expression were examined by Nissl staining and Western blot. According to our findings, high-dose NEPO improved autism-associated phenotypes. Neuroprotective effects of EPO and NEPO have been shown in the hippocampus. Postnatal NEPO treatment reversed KCC2 expression abnormalities induced by prenatal VPA. Our results might support the role of KCC2 in ASD and the excitatory/inhibitory imbalance hypothesis. We suggested Nano- erythropoietin and other KCC2 interventions as a new approach to the early treatment and prevention of autism.

Genetic ablation of metabotropic glutamate receptor 5 in rats results in an autism-like behavioral phenotype

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by deficits in communication, and social skills, as well as repetitive and/or restrictive interests and behaviors. The severity of ASD varies from mild to severe, drastically interfering with the quality of life of affected individuals. The current occurrence of ASD in the United States is about 1 in 44 children. The precise pathophysiology of ASD is still unknown, but it is believed that ASD is heterogeneous and can arise due to genetic etiology. Although various genes have been implicated in predisposition to ASD, metabotropic glutamate receptor 5 (mGluR5) is one of the most common downstream targets, which may be involved in autism. mGluR5 signaling has been shown to play a crucial role in neurodevelopment and neural transmission making it a very attractive target for understanding the pathogenesis of ASD. In the present study, we determined the effect of genetic ablation of mGluR5 (Grm5) on an ASD-like phenotype using a rat model to better understand the role of mGluR5 signaling in behavior patterns and clinical manifestations of ASD. We observed that mGluR5 Ko rats exhibited exaggerated self-grooming and increased marble burying, as well as deficits in social novelty. Our results suggest that mGluR5 Ko rats demonstrate an ASD-like phenotype, specifically impaired social interaction as well as repetitive and anxiety-like behavior, which are correlates of behavior symptoms observed in individuals with ASD. The mGluR5 Ko rat model characterized in this study may be explored to understand the molecular mechanisms underlying ASD and for developing effective therapeutic modalities.

Postweaning social isolation and autism-like phenotype: a biochemical and behavioral comparative analysis

Adolescence is a critical period for brain development. In most mammalian species, disturbances experienced during adolescence constitute a risk factor for several neuropsychiatric disorders. In this study, we compared the biochemical and behavioral profile induced by postweaning social isolation (PWSI) in inbred C57BL/6N mice with that of BTBR mice, a rodent model of autism spectrum disorders. Male C57BL/6N mice were either housed in groups of four or isolated from weaning (postnatal day 21) for four weeks before experimental analyses. After weaning, male BTBR mice were housed four per cage and analyzed at 48 days of age. PWSI reduced hippocampal levels of type 2 metabotropic glutamate (mGlu2) receptors, and glucocorticoid and mineralocorticoid receptors. A similar reduction was seen in group-housed BTBR mice. Plasma corticosterone levels in basal conditions were not influenced by PWSI, but were increased in BTBR mice. Social investigation (total and head sniffing) and the number of ultrasonic vocalizations were reduced in both PWSI mice and age-matched group-housed BTBR mice, indicating a lower social responsiveness in both groups of mice. These results suggest that absence of social stimuli during adolescence induces an endophenotype with social deficit features, which mimics the phenotype of a mouse model of autism spectrum disorders.

ASD-like behaviors, a dysregulated inflammatory response and decreased expression of PLP1 characterize mice deficient for sialyltransferase ST3GAL5

Gangliosides are glycosphingolipids, which are abundant in brain, are known to modulate ion channels and cell-to-cell communication. Deficiencies can result in aberrant myelination and altered immune responses, which can give rise to neurodevelopmental psychiatric disorders. However, to date, little mechanistic data is available on how ganglioside deficiencies contribute to the behavioural disorders. In humans, the loss of lactosylceramide-alpha-2,3-sialyltransferase (ST3Gal5) leads to a severe neuropathology, but in ST3Gal5 knock-out (St3gal5−/−) mice the absence of GM3 and associated a-, b- and c-series gangliosides is partially compensated by 0-series gangliosides and there is no overt behavioural phenotype. Here, we sought to examine the behavioural and molecular consequences of GM3 loss more closely. Mutants of both sexes exhibited impaired conditioned taste aversion in an inhibitory learning task and anxiety-like behaviours in the open field, moderate motor deficits, abnormal social interactions, excessive grooming and rearing behaviours. Taken together, the aberrant behaviours are suggestive of an autism spectrum disorder (ASD)-like syndrome. Molecular analysis showed decreased gene and protein expression of proteolipid protein-1 (Plp1) and over expression of proinflammatory cytokines, which has been associated with ASD-like syndromes. The inflammatory and behavioural responses to lipopolysaccharide (LPS) were also altered in the St3gal5−/− mice compared to wild-type, which is indicative of the importance of GM3 gangliosides in regulating immune responses. Together, the St3gal5−/− mice display ASD-like behavioural features, altered response to systemic inflammation, signs of hypomyelination and neuroinflammation, which suggests that deficiency in a- and b-series gangliosides could contribute to the development of an ASD-like pathology in humans.

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St3gal5−/− mice exhibit aberrant social, motor and cognitive behavior that is reminiscent of ASD-like syndrome.

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Interleukin1β is upregulated in the brain and spleen of St3gal5−/− of both sexes.

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Mutants display reduced gene and protein expression of the myelin protein Plp1.

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LPS induces sex-dependent abnormalities in the inflammatory response and social behavior in the St3gal5−/− mice.

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St3gal5−/− mice can be used to study the behavioural consequence of a- and b-series ganglioside deficiency