assessed by comparing the input and output relationship of the fEPSPs recorded. For each animal, we measured the fiber volley amplitude and initial slope of the fEPSP responses to a range of stimulation from 100 to 900 μA, and the stimulus intensity was adjusted individually for each experiment to produce fEPSPs, which are 30-40% of the maximal responses (submaximal) that could be evoked. The strength of synaptic transmission was quantified by measuring the amplitude of the peak amplitude of the fiber volley (input) and the initial slope of the fEPSP (output). The basal synaptic transmission was assessed by the input–output curve (I/O). The I/O curve was plotting all individual fEPSP slope and fiber volley values and fit data by linear regression analysis. The short-term and long-term synaptic modification will be measured by pair-pulse facilitation (PPF) and long-term potentiation (LTP), respectively. PPF will be evoked with interstimulus intervals of 50 ms at submaximal stimulus intensities. PPF is expressed as the ratio of the peak amplitude of fEPSP (second stimulation) / fEPSP (first stimulation). LTP will be induced by four tetani delivered 20 s apart, each at 100 Hz for 1 s after a 20 minutes baseline period. fEPSPs were monitored for
