The mechanisms underlying the antidepressant activity of quercetin are unknown. We investigated the effect of a quercetin-enriched diet (2 g/kg and 0.5 g/kg doses) on chronic social defeat stress (CSDS)induced depressive-like behaviors in mice. The 2 g/kg quercetin-enriched diet attenuated depressive-like behaviors when introduced before CSDS (long-term). The long-term 0.5 g/kg quercetin-enriched diet showed a trend toward behavioral improvement. The frequencies of spontaneous excitatory postsynaptic currents (sEPSCs) and spontaneous inhibitory postsynaptic currents (sIPSCs) in the mPFC and hippocampus were significantly higher in mice fed the long-term 2 g/kg quercetin-enriched diet compared with the normal diet; no difference was found in the amygdala. Quercetin-enriched diets administered concurrently and after stress induction failed to trigger these effects. A1-specific astrocyte reactivity was markedly suppressed in the microglia and astrocytes isolated from the mPFC and hippocampus of mice fed the long-term quercetin-enriched diet, but not in those who received quercetin supplementation concurrently or after CSDS. To confirm the role of astrocytes in the neuroprotective effect of quercetin, we activated astrocytes by injecting a chemogenic AAV stimulus into the mPFC and hippocampus and found that astrocyte activation during administration of the long-term quercetin-enriched diet significantly deceased the frequency of sEPSCs and sIPSCs in the mPFC and hippocampus and further attenuated quercetin-induced behavioral improvements. These findings highlight the key role of astrocyte reactivation in the regulation of quercetin neuroprotective activity and suggest that a diet high in quercetin, whether as a fruit- and vegetable-rich diet or food additive may help cope with stress. (C) 2020 Elsevier Inc. All rights reserved.