A Novel Approach of Development of Robust Animal Model for Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a multifactorial neurodevelopmental disorder. Numerous environmental risk factors have been implicated in the development of ASD in human cases, suggesting that multiple aetiological agents may contribute to developing an ASD rodent model. In this study, we have investigated the pathobiological processes and outcomes in a novel rat model of ASD that incorporates clinically relevant prenatal and perinatal insults. Specifically, a gamma-aminobutyric acid modulator, valproic acid (VPA), used for perinatal insults, and postnatal hypoxia was combined to understand the critical stages of brain development in rat pups and to explore potential causal mechanisms underlying ASD.

To develop the robust animal model for ASD using VPA and hypoxia as causative agents in combination to test other efficacious medicines for ASD in future.

A total of 16 female and 4 male Wistar rats were selected for mating, and the delivered pups were used for the study. The pregnant female animals were divided into four groups: G1: normal control group, G2: VPA group-received a single injection of VPA intraperitoneal (i.p.) on gestational day (GD) 12.5, G3: hypoxia group, rat pups were subjected to postnatal hypoxia, G4: VPA + hypoxia group, pregnant females received VPA (i.p. on GD 12.5), followed by normal delivery, after which the pups were subjected to postnatal hypoxia. Neurodevelopmental reflex tests, neurobehavioural assessments (open field test and Morris water maze) and three-chamber social interaction tests were conducted on the rat pups. Histopathological evaluation of the pups' brains was performed.

The VPA, hypoxia and combined VPA + hypoxia groups exhibited significant neurobehavioural alterations, with marked delays in neurodevelopmental reflexes compared to the normal control group. Histopathological examination of the brain revealed a reduction in Purkinje cells within the Purkinje cell layer, along with extensive neuronal degeneration. The severity of both neurobehavioural deficits and histopathological abnormalities was greatest in the combined VPA + hypoxia group compared to the other experimental groups.

These findings suggest that the combination of prenatal VPA exposure and postnatal hypoxia, representing pre- and perinatal insults, induces ASD-like conditions in rat pups that closely resemble the clinical behaviour features and redox imbalance of human ASD. Thus, this combined model could serve as a potential animal model for ASD and could be used for screening pharmacological agents aimed at treating and managing ASD.