Figure 6.

Effects of pretraining injection of compounds on fear conditioning in NCAM deficient (NCAM−/−) mice. A, Scheme showing manipulations performed in this series of experiments. Compounds were injected 4 h before training. A 100 s trial (B) was used to evaluate the baseline response to the conditioned context (CC+) before training. B, NCAM−/− mice showed robust impairment of contextual memory tested on the first and third days after training (trials 1 and 3, respectively) compared with their wild-type littermates, NCAM+/+. The deficit in contextual memory in NCAM−/− mice was partially rescued by pretraining injection of PSA-NCAM-Fc, but not by NCAM-Fc, as compared with Fc. Injections of PSA-NCAM-Fc into NCAM+/+ mice impaired contextual memory. All mice showed similar freezing responses during the baseline period (trial B). C, NCAM−/− mice were impaired in cued memory compared with NCAM+/+ mice. This deficit in NCAM−/− mice could be rescued by the pretraining injection of PSA-NCAM-Fc but not NCAM-Fc. Other groups showed no effect of treatment in cued memory processing as well as in discrimination of CS+ and CS− tones, as compared with Fc injected mice. ^#p ≤ 0.05, ^##p ≤ 0.01, ^###p ≤ 0.005, ^####p ≤ 0.001 (ANOVA); *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.005, ****p ≤ 0.001 (post hoc FLSD for comparisons indicated for ANOVA, for corresponding days); ⁺p < 0.05, ⁺⁺p < 0.01, ⁺⁺⁺p < 0.005, ⁺⁺⁺⁺p < 0.001 (Wilcoxon test).