Objective Quercetin, a flavonol compound widely distributed in fruits, vegetables, and medicinal plants, has been suggested to act as a neuroprotective agent. In the present study, we investigated the presynaptic effect of quercetin on synaptic transmission and plasticity.Methods Using whole-cell patch clamp and capacitance measurement technique, we recorded miniature excitatory postsynaptic currents (mEPSC), presynaptic calcium influx, vesicle release and recycling, and the replenishment of readily releasable pool (RRP). Additionally, we stimulated the axon with 5-200 Hz and recorded short-term depression (STD) in the postsynaptic neuron.Results We found that 100 μmol/L quercetin in the extracellular solution did not affect the mEPSC amplitude and frequency, indicating a presynaptic mechanism modulating synaptic transmission. At the presynaptic nerve terminals, 100 μmol/L quercetin did not induce notable changes in calcium influx or vesicle release, but significantly inhibited clathrin-dependent slow endocytosis following exocytosis. The inhibition of endocytosis led to a slowdown of vesicle mobilization during stimulation, a reduction in readily releasable pool replenishment after stimulation, and enhancement of short-term depression during high-frequency repetitive stimulation in the postsynaptic principal neurons.Conclusion These results provide new insights into quercetin-modulated neuronal signaling and suggest a protective effect that prevents excessive excitatory synaptic transmission in brain circuits.