Figure 1.

Post-recall NMDAR blockade hinders SDIA extinction memory and induces SDIA memory recovery. (a) Animals were trained in SDIA (TR; 0.4 mA/2 s) and beginning 24 h later they were submitted to one daily extinction training trial for 5 consecutive days. Twenty-four hours after the last extinction training trial, SDIA extinction memory was reactivated (RA) and, 5 min thereafter, the animals received bilateral intra-dorsal CA1 infusions of vehicle (VEH; 1% DMSO in saline) or the NMDAR antagonist AP5 (5 µg/side). Retention was assessed 1 day and 7 days later (Test). (b) Animals were treated as in A except that they received intra-CA1 infusions of VEH or AP5 6 h after RA. (c) Animals were treated as in A, except that RA was omitted (No RA). (d) Animals were treated as in A, but a group of them received VEH or AP5 5 min after a pseudo-reactivation extinction session (pRA) carried out in an SDIA training box modified to be non-aversive (NA) for SDIA-trained animals (test latency in SDIA: Median = 162 s; IQR = 74–244.5 s; test latency in NA: Median: 10 s; IQR = 7.5–17.5 s; U = 3.00, p = 0.0003, SDIA vs NA in Mann–Whitney test). The non-aversive box was similar in dimensions to the SDIA-training apparatus but was painted gray and the elevated platform was made of transparent plexiglass instead of wood. Data are expressed as median ± IQR. (***) p < 0.001 versus VEH in Mann–Whitney test; n = 10–12 animals per group.