The ventral tegmental area (VTA) in the ventral midbrain is the origin of the dopaminergic neurotransmission pathways. Although GABA_A receptors and AKT-GSK3β signaling are involved in the pathophysiology of mental disorders and are modulated by antipsychotics, an unmet task is to reveal the pathological changes in these biomarkers and antipsychotic modulations in the VTA. Using a juvenile polyriboinosinic-polyribocytidylic acid (Poly I:C) psychiatric rat model, this study investigated the effects of adolescent risperidone treatment on GABA_A receptors and AKT/GSK3β in the VTA. Pregnant female Sprague–Dawley rats were administered Poly I:C (5mg/kg; i.p) or saline at gestational day 15. Juvenile female offspring received risperidone (0.9 mg/kg, twice per day) or a vehicle from postnatal day 35 for 25 days. Poly I:C offspring had significantly decreased mRNA expression of GABA_A receptor β3 subunits and glutamic acid decarboxylase (GAD2) in the VTA, while risperidone partially reversed the decreased GAD2 expression. Prenatal Poly I:C exposure led to increased expression of AKT2 and GSK3β. Risperidone decreased GABA_A receptor β2/3, but increased AKT2 mRNA expression in the VTA of healthy rats. This study suggests that Poly I:C-elicited maternal immune activation and risperidone differentially modulate GABAergic neurotransmission and AKT-GSK3β signaling in the VTA of adolescent rats.