Ultrastructural localization of the δ2 glutamate receptor in wild-type and mutant cerebellum. Immunogold labeling of parallel fiber/Purkinje cell spine synapses, with delta 1/2 antibody, in cerebella from PSD-93 knock-out (KO) and wild-type (WT) mice. p, presynaptic terminal. Scale bar, 0.2 μm.