Memory consolidation and reconsolidation in GSK-3β heterozygous mice.

Memory consolidation and reconsolidation were assessed with a contextual fear-conditioning (CFC) test following the schedule shown in A. Mice were placed in a novel environment (plastic chamber) for 5 min (conditioning stimulus, CS), where they received three electrical foot shocks (unconditioning stimulus, US; shock intensity = 0.5 mV; duration = 2 sec; inter-stimuli interval = 60 sec). In the consolidation test performed 7 days later, the mice (WT littermates, n = 13; GSK^+/−, n = 14; 7–14 months old) were placed into the plastic chamber again for 5 min without receiving stimulation, and freezing time was measured (A, B). In the reconsolidation test performed on day 1 and day 7 of training, the mice (WT littermates, n = 17; GSK^+/−, n = 11) were placed into the plastic chamber again for 5 min without receiving stimulation, and freezing time was measured (A, C–E). On day 7 of the consolidation test (B), the freezing times of WT littermate (white bar) and GSK^+/− (black bar) mice were not significantly different (p = 0.437, Mann-Whitney test). However, on day 7 of the reconsolidation test, the freezing times of GSK^+/− mice had decreased significantly compared to that of their WT littermates (c; p = 0.0026, Mann-Whitney test). Comparison of day 1 and day 7 freezing times of WT littermate (D) and GSK^+/− (E) mice revealed that, on day 7 of the reconsolidation test, GSK^+/− mice showed significantly reduced freezing times (p = 0.0095, Mann-Whitney test), while WT littermate mice did not (p>0.0733, Mann-Whitney test). Results are expressed as means±SEM; **, p<0.01.