NMDAR agonist and antagonist treatments differentially affect the behavioral transition between reconsolidation and extinction. A, Experimental design. One day after training, the rats received an intraperitoneal injection of the NMDAR partial agonist DCS (15 mg/kg) or the antagonist MK-801 (0.1 mg/kg). B–E, One quarter of each group received 1 CS (B), 4 CS (C), 7 CS (D), or 10 CS (E) presentations (line graphs). Twenty-four hours later, freezing behavior was measured in all groups by the presentation of one CS (bar graphs). Data are presented as means ± SEM. MK-801 groups: 1 CS, n = 12; 4 CSs, n = 9; 7 CSs, n = 9; and 10 CSs, n = 11. DCS groups: 1 CS, n = 7; 4 CSs, n = 8; 7 CS, n = 8; and 10 CSs, n = 8. *p < 0.05, **p < 0.01.