Genetic and pharmacological evidence linking CB1R signaling to hippocampal GABAergic dysfunction in ASD mouse model.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder increasingly linked to disrupted GABAergic inhibition and altered excitatory-inhibitory balance. Cannabinoid receptor 1 (CB1R), enriched on GABAergic interneurons, modulates inhibitory tone. Whether CB1R dysfunction in GABAergic neurons contributes to ASD-like phenotypes remains unclear. This study investigated the role of CB1R in GABAergic regulation and evaluated whether pharmacological CB1R activation could ameliorate GABAergic abnormalities and behavioral deficits in ASD models. We generated conditional CB1R knockout mice in GABAergic neurons (GABA-CB1-/-) and performed behavioral and molecular ultrastructural analyses. GABAergic and neuronal alterations were quantified in hippocampus and striatum by Western blotting, immunofluorescence, and transmission electron microscopy. SA-PEG-DSPE nanomicelles were used to deliver the CB1R agonist ACPA or in combination with the GABAA receptor agonist muscimol to valproic-acid (VPA)-exposed mice to assess pharmacological modulation. GABA-CB1-/- mice exhibited social deficits, spatial learning and memory impairments, and repetitive behaviors similar to those of VPA mice. Both models showed increased GAD67 and GABARAP, reduced ABAT, a lower PSD95/gephyrin ratio, a reduced proportion of GAD67+NeuN + neurons, marked dendritic and synaptic disruption in the hippocampus, whereas changes in the striatum were limited. Nanomicelle-mediated ACPA administration ameliorated GABAergic molecular alterations, improved dendritic integrity and ASD-like behaviors, whereas, muscimol co-administration partially attenuated these effects in VPA mice. CB1R deficiency in GABAergic neurons was associated with ASD-like phenotypes accompanied by hippocampal GABAergic dysfunction. Pharmacological CB1R activation ameliorated behavioral and molecular abnormalities, while modulation of GABAAR partially attenuated these effects. These findings support further investigation of CB1R as a potential therapeutic target for ASD.