A, distribution of GluR2 immunofluorescence (in green) in the Purkinje cell plate of an E19 embryo (single confocal section). Lowers panels are enlargements of the boxed area. Most immunoreactive puncta (some indicated by arrowheads in the lower panels) are apposed to presumptive axon terminals (identified by synaptophysin immunoreactivity, in red). The double arrow in the lower panels indicates a GluR2 immunoreactive puncta apparently not apposed to synaptophysin labelling. B, distribution of GluR2 immmunofluorescence (in green) in the Purkinje cell plate of an E20 embryo (single confocal sections). Virtually all GluR2-containing AMPA receptor clusters are apposed to the presynaptic markers synaptophysin (left panel, red) and VGluT2 (right panel, red). C, developmental translocation of GluR2-containing AMPA receptor clusters (green) on the cell bodies and dendrites of Purkinje cells identified by calbindin immunolabelling (in red). Note the increased intracellular expression of GluR2 at P4–P7.