In rat neurons, NMDA receptors that contain GluN3A (Grin3a) or GluN3B (Grin3b) subunits, traffic to the plasma membrane to the perisynaptic regions, located at the periphery of the postsynaptic density (PSD). GluN3a and GluN3b do not have PDZ-binding domains and thus do not interact directly with PSD-95 family members. A small fraction of GluN3-containing NMDA receptors that localize to the central region of the PSD may be tri-heteromers with GluN2 subunits (Perez-Otano et al. 2006, Wee et al. 2016).