(A) Disruptive effect of temporary prelimbic (PL) cortex inactivation induced by muscimol (MUS) on fear memory reconsolidation. After a familiarization (Fam.) session, animals had Context A paired with foot shocks, the unconditioned stimulus (US). On the next day, they were reexposed to Context A to retrieve/reactivate the established memory, and then received bilaterally into the PL cortex MUS (4.0 nmol in 0.2 µL per side) or vehicle (VEH). Relative to controls, MUS-treated animals froze less when reexposed to the paired context 1 d later (Test A). No differences between groups were seen in an unpaired context (Test B). (B) Fear memory reactivation was necessary for reconsolidation blockade induced by PL-cortex inactivation to occur. On the day following the contextual conditioning session described above, the animals were infused with MUS or VEH after being exposed to Context B (unpaired context) for 3 min. No differences were found when they were reexposed to the paired Context 24 h later (Test A). (C) Bilateral infusion of MUS (4.0 nmol in 0.2 µL per side) into the infralimbic (IL) cortex after memory retrieval/reactivation did not change freezing time relative to the respective controls during both Tests A and B. Gray arrowheads indicate the moment of drug treatment. Bars represent the percentage of total time spent freezing. Values are expressed as mean ± SEM. (*) Significant difference (P < 0.05) compared with the respective controls (repeated-measures ANOVA followed by Newman–Keuls test).
