In the developing hippocampus experiments using whole-cell recordings have shown that a small number of synaptic activations can convert many glutamate synapses to AMPA silent synapses. This depression of AMPA signaling is induced by low frequency (0.05 - 0.2 Hz) activation, does not require NMDA or metabotropic glutamate receptor activation for its induction, and does not readily reverse following stimulus interruption. Here we show, using field recordings and perforated patch-clamp recordings of transmission in developing CA3 - CA1 synapses, that this synaptic depression also can be observed under more non-invasive recording conditions. Moreover, under these conditions the synaptic depression spontaneously recovers within 20 minutes by the absence of synaptic activation alone, with a time constant of about 7 minutes as determined by field EPSP recordings. Thus, as for the expression of long-term potentiation, recovery from this depression is susceptible to whole-cell dialysis ("wash-out"). In contrast to LTP-induced unsilencing, the AMPA signaling following stimulus interruption was again labile, resumed stimulation resulted in renewed depression. The present study has thus identified a novel cycle for AMPA signaling in which the nascent glutamate synapse cycles between an AMPA silent state, induced by a small number of synaptic activations, and a labile AMPA signaling, induced by prolonged inactivity.