Presynaptic properties of synapses contacting developing and mature GCs. (A) Typical responses to paired-pulse stimulation delivered at the proximal site. Top: Mean responses for the whole dataset (all successes and failures). Middle: Mean potency values for responses to the first and second rounds of stimulation (successful responses only). Bottom: AMPAR-mediated EPSC amplitude and potency. AMPAR-mediated EPSC amplitude for responses to the second round of stimulation, after AMPAR-mediated EPSCs amplitude to first stimulation was scaled (black) to potency for AMPAR-mediated EPSCs amplitude (gray). Scale bar = 10 ms and 10 pA. (B) Paired-pulse ratios for successful responses (left) (ten slices, six mice) and AMPAR-mediated EPSC amplitude (right), recorded from mature GCs (10 slices, six mice). (C) Left: Potency ratio (successful responses only) plotted as a function of AMPAR-mediated EPSCs amplitude ratio (successes and failures) recorded from mature GCs. Most points fell on or near the horizontal dashed line. The linear regression line fitted to all data points is shown in black. P < 0.05 indicates significant deviation of the slope from zero. Right: Comparison between observed (exp) Yes and predicted (Poisson) potency ratios. Predicted values were obtained using a Poisson model. Data were for mature GCs. (D) Ratio of AMPAR-mediated to NMDAR-mediated EPSC amplitude increased during the early developmental stage (class 3 versus class 4, class 4 versus mature; *P < 0.05) (class 3: six slices, six mice; class 4: nine slices, eight mice; class 5: four slices, four mice; mature: six slices, five mice).