N-methyl-D-aspartate receptors (NMDAR) are gluta mate gated ion channels mediating the vast majority of excitatory neurotransmission in central neural system.NR3 is recently dis covered subunits of NMDAR, and has been shown to reduce the calcium permeability when is involved in NMDAR.Since Ca2+influx through NMDAR-operated channels is considered as pre dominant reason to induce excitotoxicity, NR3 subunits may pro vide a protective role by depressing calcium overloading.In the present study, it was found that the expression of NR3A protein on rat hippocampus began to increase on the postnatal days,which reached the highest expression level on post natal day 10,and decreased gradually, which remained low into the adulthood.