The rhythms of local field potentials (LFPs) are reported to be related to cognition whose underling mechanism is synaptic plasticity.Our study explored whether the coupling direction of neural information flow (NIF) could be used to characterize the synaptic plasticity in hippocampal CA3-CA1 pathway and examined which rhythm was most relevant in melamine-treated rats.Male Wistar rats orally administered melamine at a dose of 300 mg/kg.day 1 for 4 weeks to setup an animal model.General partial directed coherence (gPDC) was employed to measure directional indexes between CA3 and CA1 at five rhythms using LFPs collected before longterm potentiation (LTP) induction.Results show that index d > 0 indicating the NIF flowed from CA3 to CA1 in both groups.The unidirectional index CCA3→CA1 reduced remarkably at θ and γ rhythms consistent with the reduced LTP in melamine-treated rats.It suggests that the directional index at θ and γ rhythms could character the synaptic plasticity.