(A–D) c-fos induction when IA memory is enhanced after reactivation. (A) Representative immunohistochemical staining of BA, CA3, and PL c-fos-positive cells from the indicated group. Scale bar, 50 μm. Two groups were trained with a footshock: one group received memory reactivation (T/R), while the other group did not (T/NR). The remaining two groups did not receive a footshock. During the Reactivation session, the animals were returned to the light compartment (U/R) or not (U/NR). (B–D) c-fos expression in the LA, BA, and CeA regions of the amygdala (B), CA1, CA3, and DG regions of the hippocampus (C), and PL and IL of the mPFC (D) (n = 13–21 for each group). (E–G) Effects of anisomycin micro-infusions immediately after Reactivation in the amygdala (E, VEH, n = 8, ANI, n = 9), hippocampus (F, VEH, n = 10, ANI, n = 10), and mPFC (G, VEH, n = 10, ANI, n = 11). Micro-infusion of ANI into the amygdala blocked IA memory as seen by the reduction in performance between Reactivation and PR-LTM. In contrast, micro-infusion of ANI into the hippocampus or mPFC blocked the enhancement, but not the underlying performance. (H and I) Phosphorylation of GluA1 at Ser831 and Ser845 was induced in the amygdala, hippocampus, and mPFC following memory retrieval. (H) Representative western blot analysis of the amygdala, hippocampus, and mPFC showing phosphorylated GluA1 and total GluA1 levels. (I) Levels of Ser831 and Ser845-phosphorylated GluA1 in the amygdala, hippocampus, and mPFC (n = 9 per group). The levels of Ser831- and Ser845-phosphorylated GluA1 for each group are expressed as the ratio of the U/NR group to the other groups. ANI: anisomycin; BA: basolateral amygdala; CeA: central amygdala; DG: dentate gyrus; IA: inhibitory avoidance; IL: infralimbic region; LA: lateral amygdala; mPFC: medial prefrontal cortex; PL: prelimbic region; PR-LTM: post-reactivation long-term memory test; VEH: vehicle. Error bars, SEM. *p<0.05, compared with the other control groups (B–D and I). **p<0.005; paired t test (E–G). The results of the statistical analyses are presented in Figure 2—source data 1.