Resveratrol Prevents Behavioral Changes in the Valproic Acid-Induced Animal Model of Autism, Modulating Excitation/Inhibition Balance in Mpfc and Hippocampus

Background: Autism spectrum disorder (ASD) is a neurodevelopmental disability characterized by sociability impairments accompanied by communication deficits and stereotyped behavioral patterns. Although ASD etiology is still not known, there is growing evidence that an imbalance between excitation and inhibition is a prominent characteristic at the neuronal circuitry level. One of the known risk factors for ASD is maternal use of valproic acid (VPA) during gestation. Based on this observation, VPA is commonly used to generate an ASD-like condition in rodents.

Objectives: Considering the neuroprotective, antioxidant and anti-inflammatory effects of resveratrol (RSV), we aimed to investigate the influence of prenatal RSV treatment on a set of social behaviors. In addition, we assessed the influence of this treatment on mRNA and protein expression levels of excitatory (PSD-95 and neuroligin-1) and inhibitory (gephyrin and neuroligin-2) synaptic proteins in medial prefrontal cortex (mPFC) and hippocampus.

Methods: Pregnant females were randomly divided into four groups: Control, RSV, VPA and VPA + RSV. Valproic acid (600 mg/Kg) was injected intraperitoneally on embryonic day 12.5 (E12.5). Resveratrol (3.6 mg/kg) was administered subcutaneously every day from E6.5 to E18.5. Control group received only vehicle. Social behavior was assessed through social transmission of food preference (STFP) in young male rats and by three chamber and empathy tests in adults. Two animals per litter of at least 4 litters were tested. Levels of synaptic proteins were determined using qRT-PCR and Western blot analysis. Statistical analysis was performed using the SPSS 20 Software. Two-way ANOVA was used for all tests, except the three-chamber, which was analyzed by a generalized estimating equation (GEE).

Results: In the three-chamber test, VPA rats presented no preference between a new object and a new rat and no preference for social novelty. Prenatal administration of resveratrol prevented these VPA-induced social impairments. In the STFP, VPA animals showed impaired communication, as indicated by the absence of preference for the flavored food consumed by the demonstrator rat. RSV treatment again averted VPA action, but interestingly switched the preference toward the new flavor. The empathy test revealed that VPA rats have a delay in the first opening of the restrainer to release the trapped conspecific to in comparison to controls. However, once they start opening the restrainer, they opened it in the subsequent days. Resveratrol did not change this pattern. For the expression analysis, we found that RSV led to a trend of decrease in the level of protein PSD-95 in the mPFC of the VPA+RSV group animals compared to the VPA group (p=0,092), probably exerting its actions at the translation level. In addition, RSV increased gene expression of gephyrin in both mPFC and hippocampus.

Conclusions:   Therefore, the present study demonstrates a successful prenatal intervention able to prevent social alterations induced by VPA in rats. In addition, we identified possible mechanisms by which RSV could diminish neuronal excitability. This can be the basis for the phenotypic prevention exerted by RSV and adds evidence to the growing body of findings that behavioral alteration can be mediated by excitation/inhibition regulation in ASD.