Fig. 5

Effect of purine metabolite administration on fear memory. a Fear conditioning protocol (DS, same as in Figs. 2a and 4). Post-shock period denotes the 30-s period after the tone and shock toward the end of the session. b Shock reactivity during conditioning (one-way ANOVA, p > 0.05, error bars, 95% CIs). Freezing in post-shock period (c) and the context test (d), and the tone test (e; blue shade, timing of tone exposure) (one-way ANOVA, p > 0.05, error bars, 95% CIs). f Discrimination between the context used for the context test and that used for the tone test (Kruskal–Wallis test, p > 0.05, error bars, 95% CIs). g–p Correlations between freezing in post-shock period and freezing during the context test (g–k or tone test (l–p, during the first min of tone exposure). q–u Correlations between freezing in the third tone period (except the 2-s of shock period) and freezing during tone test. Two-tailed Pearson’s correlation coefficients, p-values indicated in each plot; trend lines, linear regression (g-u). Control, n = 16 mice; hypoxanthine, n = 12; xanthine, n = 13; allantoin, n = 19; urea, n = 16