Schematic illustration of the sequence of events involved in the generation of inhibitory signals at BC output synapses in the young and the mature dentate gyrus of GAD67–GFP mice. From left to right: a somatic action potential, axonal action potential propagation, time course of quantal transmitter release, and unitary IPSCs in young (top) and mature (bottom) networks are shown. The percent change of the given property of BC signaling at young (P6–P10) and mature (P18–P25) developmental stages is shown in brackets. Note that the combination of changes in these parameters underlies the emergence of fast signaling properties in BCs during development. See Results and Discussion for details. half-dur., Half-duration; conduc. time, conduction time; peak amp., peak amplitude.