Metyrapone paired with a single extinction trial enhances memory retrieval. Mice injected with metyrapone 90 min prior to reactivation show enhanced fear memory retrieval, compared to controls [mixed ANOVA, main effect of group F(1, 18) = 7.29, p = 0.015; main effect of day F(2, 36) = 99.83, p < 0.000001, group × - day interaction F(2, 36) = 3.59, p = 0.038], post hoc comparisons (Fisher LSD) of days 0 (training) and 1 (Veh. vs Met.., p = 0.79, p < 0.0000001, respectively). However, one injection of metyrapone was not sufficient to sustain this enhancement in memory retrieval 24 h later (post hoc comparisons, Fisher LSD; probe day 2, p = 0.133). N = 10 for all groups.