Antidepressant effects of combination of brexpiprazole and fluoxetine on depression-like behavior and dendritic changes in mice after inflammation

RATIONALE: Addition of low doses of atypical antipsychotic drugs with selective serotonin reuptake inhibitors (SSRIs) could promote a rapid antidepressant effect in treatment-resistant patients with major depression. Brexpiprazole, a new atypical antipsychotic drug, has been used as adjunctive therapy for the treatment of major depression. OBJECTIVES: The present study was undertaken to examine whether brexpiprazole could augment antidepressant effects of the SSRI fluoxetine in an inflammation model of depression. METHODS: We examined the effects of fluoxetine (10 mg/kg), brexpiprazole (0.1 mg/kg), or the combination of the two drugs on depression-like behavior, alterations in the brain-derived neurotrophic factor (BDNF) - TrkB signaling, and dendritic spine density in selected brain regions after administration of lipopolysaccharide (LPS) (0.5 mg/kg). RESULTS: Combination of brexpiprazole and fluoxetine promoted a rapid antidepressant effect in inflammation model although brexpipazole or fluoxetine alone did not show antidepressant effect. Furthermore, the combination significantly improved LPS-induced alterations in the BDNF - TrkB signaling and dendritic spine density in the prefrontal cortex, CA3 and dentate gyrus, and nucleus accumbens. CONCLUSIONS: These results suggest that add-on of brexpiprazole to fluoxetine can produce a rapid antidepressant effect in the LPS inflammation model of depression, indicating that adjunctive therapy of brexpiprazole to SSRIs could produce a rapid antidepressant effect in depressed patients with inflammation.