A, an example of complete serial ultrathin sections (70 nm thickness) of a P3 CF-Purkinje cell synapse. Arrows indicate edges of the PSD. B, immunogold labelling by anti-GluR2/3 antibody was localised within PSDs of CF-Purkinje cell synapses. C, histograms of the PSD area (top) and of the quantal size (bottom). Pooled data of 1112 MEPSCs recorded at 33–34 °C from four cells, and of 122 randomly sampled PSDs, are shown.