Fig. 3. As in rat spinal cord, both α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N -methyl-d-aspartate (NMDA) receptors contribute to excitatory postsynaptic currents (EPSCs) in mouse motor neurons. (A ) The glutamate NMDA antagonist D,L-2-amino-5-phosponopentanoic acid (50 μm) reduced the size of the synaptic currents, which were blocked completely by addition of the AMPA-kainate antagonist 6-cyano-7-nitroquinoxaline-2,3-dione disodium (10μm), indicating that the remaining fast-decaying EPSC was mediated by AMPA-kainate receptors. The blockade was reversible after washout. Each EPSC trace shown here is an average of five consecutive responses. (B ) In the same cell, the sequence of application of glutamate antagonists was reversed. The slow-rising and slow-decaying EPSC in the presence of 6-cyano-7-nitroquinoxaline-2,3-dione disodium was blocked further by addition of D,L-2-amino-5-phosponopentanoic acid indicating the slow-decaying EPSC was mediated by NMDA receptors. (C ) The amplitude of EPSCs recorded from this motor neuron versus  time. Block by each antagonist was completely reversible in the presence of the other.