A mouse model of anxiety/depression-like behavior was induced by chronic corticosterone treatment, and chronic antidepressant treatment reversed the behavioral dysfunctions and inhibited hippocampal neurogenesis. Fluoxetine's efficacy was partially blocked in some behavioral paradigms when hippocampal neurogenesis was ablated by X-irradiation, suggesting both neurogenesis-dependent and independent mechanisms of antidepressant action. Candidate genes, including β-arrestin 2, were identified whose expression was decreased by chronic corticosterone and normalized by chronic fluoxetine treatment. Mice deficient in β-arrestin 2 showed reduced response to fluoxetine, indicating that β-arrestin signaling is necessary for its antidepressant effects. The study also demonstrated that chronic fluoxetine treatment restored normal levels of β-arrestin 1, β-arrestin 2, and Gia2 mRNA in the hypothalamus but not in the amygdala or hippocampus. β-arrestin 2 knockout mice displayed reduced response to fluoxetine in anxiety-related tasks, suggesting that β-arrestin 2 is essential for fluoxetine's anxiolytic/antidepressant effects. The findings highlight the role of both neurogenesis-dependent and -independent mechanisms in the antidepressant effects of fluoxetine, with β-arrestin signaling playing a critical role. The study provides insights into the molecular mechanisms underlying antidepressant action and the potential for developing new treatments targeting these pathways.A mouse model of anxiety/depression-like behavior was induced by chronic corticosterone treatment, and chronic antidepressant treatment reversed the behavioral dysfunctions and inhibited hippocampal neurogenesis. Fluoxetine's efficacy was partially blocked in some behavioral paradigms when hippocampal neurogenesis was ablated by X-irradiation, suggesting both neurogenesis-dependent and independent mechanisms of antidepressant action. Candidate genes, including β-arrestin 2, were identified whose expression was decreased by chronic corticosterone and normalized by chronic fluoxetine treatment. Mice deficient in β-arrestin 2 showed reduced response to fluoxetine, indicating that β-arrestin signaling is necessary for its antidepressant effects. The study also demonstrated that chronic fluoxetine treatment restored normal levels of β-arrestin 1, β-arrestin 2, and Gia2 mRNA in the hypothalamus but not in the amygdala or hippocampus. β-arrestin 2 knockout mice displayed reduced response to fluoxetine in anxiety-related tasks, suggesting that β-arrestin 2 is essential for fluoxetine's anxiolytic/antidepressant effects. The findings highlight the role of both neurogenesis-dependent and -independent mechanisms in the antidepressant effects of fluoxetine, with β-arrestin signaling playing a critical role. The study provides insights into the molecular mechanisms underlying antidepressant action and the potential for developing new treatments targeting these pathways.