There is presently an argument regarding the receptor composition of glutamate synapses in the developing brain.On one hand,spontaneous AMPA and NMDA EPSCS appear in approximately equal proportions during the two postnatal weeks,suggesting that the newly formed synapses contain both AMPA and NMDA receptors.On the other hand,evoked activation of these synapses often results in only NMDA EPSCs,and no AMPA ones.It has led to the common notion that glutamate synapses are formed with only NMDA receptors in neonatal animal brain.The above discrepancy could be settled if the nascent glutamate synapse is prone to an activity-dependent depression of AMPA EPSCs.In the present study,we have investigated the influences of test frequency (0.05 Hz) stimulation on the EPSCs at rat neonatal CA3-CA1 synapses.We made whole cell recording from CA1 pyramidal neurons (from rats at postnatal day 10-12,P10-P12) voltage-clamped at-70 mV.EPSCs were evoked at 0.05 Hz using a pre-set stimulus intensity.Stimulation of Schaffer collateral afferent was performed using a pipette filled with ACSF (resistance ~1 MΩ).