Prenatal Valproate Exposure Affects Cortical Neurite Branching, GABAergic Markers, Motor Reflexes and Ultrasonic Vocalizations in the Male Rat Pups

Abstract

Autism spectrum disorder (ASD) is a complex neurodevelopmental condition, characterized by early-onset deficits in social interactions, communication, and repetitive behaviors. Dysfunction of gamma-aminobutyric acid (GABA) neurotransmission during neural development has been implicated as a potential mechanism, particularly within the frontal cortex. This study aimed to investigate the effects of prenatal valproate (VPA) exposure on the sensorimotor reflexes, ultrasonic vocalization (USV), and GABAergic markers in the frontal cortex of male offspring. The morphology of primary cortical neurons isolated from control and prenatally VPA-exposed rats was also assessed. Significant sensorimotor developmental delays were observed in VPA-exposed male rats, evident from delays in negative geotaxis and righting reflex tests on postnatal Day 5. The recordings of USV calls showed significant decreases in both the total number of calls and average call duration. Increased gene expression of glutamate decarboxylase 2 (Gad65), vesicular GABA transporter (Vgat), GABAA receptor β subunit 1 (Gabrb1), and Gabarap-like protein 1 (Gabarapl1) was found in the frontal cortex of VPA-exposed pups, indicating alterations in the GABAergic system. Total primary cortical neurons and parvalbumin-positive neurons from VPA-exposed pups showed reduced branching and shorter neurites, whereas GABAergic neurons exhibited increased arborization, and somatostatin-positive neurons showed no change. These findings suggest that prenatal VPA exposure alters cortical neuron morphology and GABAergic markers, potentially contributing to motor and early vocal communication impairments, which may explain the etiology of specific autistic symptoms.