ASD is a developmental disorder with core symptoms of social impairments and restrictive repetitive behaviors. Its prevalence in a male is 4-times higher than in the female. Dysfunction in the GABAergic system has been implicated in ASD but the exact cause is unclear yet. Thus, no appropriate drugs are currently available for ASD. We recently found that SKF105111 (SKF), a type I 5α-reductase inhibitor, reduced the brain level of allopregnanolone (ALLO), a positive allosteric GABAA receptor modulator and thereby caused ASD-like behaviors only in male mice, suggesting that SKF treatment provides a novel animal model of ASD. Moreover, to elucidate if Kamishyoyosan (KSS), a Kampo formula used for the treatment of neuropsychiatric symptoms in the menopause female, is available for ASD therapy, we examined the effects of KSS on ASD-like behaviors in the ALLO deficient mouse model. KSS ameliorated sociability deficits via improving the mechanisms mediated by the dopamine D1 receptor, while it reduced repeated grooming behaviors via improving the mechanisms mediated by dopamine D1 and D2 receptors and the GABAA receptors. Our findings suggested that KSS is beneficial for the treatment of ASD.

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