Cue-induced cocaine craving progressively intensifies (incubates) after withdrawal from cocaine self-administration in rats and humans. In rats, the expression of incubation ultimately depends on Ca2+-permeable AMPARs (CP-AMPARs) that accumulate in synapses onto medium spiny neurons (MSN) in the nucleus accumbens (NAc) core. However, the delay in their accumulation (approximately 1 month after drug self-administration ceases) suggests earlier waves of plasticity. This prompted us to conduct the first study of NMDAR transmission in NAc core during incubation, focusing on the GluN3 subunit, which confers atypical properties when incorporated into NMDARs including insensitivity to Mg2+ block and Ca2+-impermeability. Whole-cell patch-clamp recordings were conducted in MSNs of adult male rats 1-68 days after discontinuing extended-access saline or cocaine self-administration. NMDAR transmission was enhanced after 5 days of cocaine withdrawal and this persisted for at least 68 days of withdrawal. The earliest fu...