Synaptic localization of NMDA receptor subunits in the stratum radiatum of hippocampal CA3 region. Postembedding immunogold labeling for GluN2A (A, B), GluN2B (C, D), GluN1-C2 (E, F), GluN1-C2′ (G, H), and PSD-95 (I, J) in the stratum radiatum of control and mutant CA3 region. NT, Nerve terminal; Sp, spine. Scale bar, 100 nm.