The hippocampus is known to play a major role in the storage and recall of information depending on various forms of activity dependent synaptic plasticity. Mossy fiber synapses between the axons of dentate gyrus (DG) granule cells and CA3 pyramidal cells (Mf-CA3 synapses) display a high dynamic range of presynaptic plasticity which endow these synaptic connections with detonator properties. The pattern of action potential firing, in the form of high frequency bursts in the DG, strongly controls the amplitude of synaptic responses and information transfer to CA3. Presynaptic short-term plasticity is thought to play a major role in the process of spike transfer within local circuits. We have investigated the role of presynaptic facilitation at Mf-CA3 synapses in the operation of CA3 circuits in vivo and in memory encoding. We have selectively abrogated Syt7, a calcium sensor necessary for presynaptic facilitation, in DG granule cells using conditional Syt7 KO mice. In hippocampal slices, we extend previous analysis to show that short-term presynaptic facilitation is selectively suppressed at Mf-CA3 synapses in the absence of Syt7. We next use simultaneous silicon probe recordings in the DG and CA3 to address how the network adapts to abrogation of presynaptic plasticity, in reference to brain oscillations. This approach brings new understanding of the role in presynaptic facilitation and specifically on the detonator properties of DG-CA3 synapses.