A, application of NMDA (3 μm) in the presence of glycine (5 μm) to the outside-out patch isolated from a PND 10 motoneuron voltage clamped at −100 mV induced single-channel currents to four different amplitude levels. Examples of NMDA-induced single-channel openings to each of the four conductance levels identified. Dotted lines show where the current levels identified from the fit of the amplitude distribution would fall. The distribution of channel amplitudes of openings longer than 0.425 ms was fitted with the sum of 4 Gaussian components of amplitude (relative area): −2.0 pA (9%), −3.9 pA (9%), −5.9 pA (45%), −6.9 pA (37%). B, comparison of conductances of motoneuron and recombinant NMDA receptor channels: aPaleček et al. (1999); bStern et al. (1992, 1994); cStern et al. (1992), Wyllie et al. (1996).