Fig. 1: Rapid forgetting of social recognition memory is enhanced by Rac1(CA) in PV but not SST neurons of the brain.

a Parvalbumin (PV)-Cre or somatostatin (SST)-Cre mice were crossed with Rac1-loxp mice containing a constitutive activation (CA) of Rac1 mutation, and only PV-Rac1(CA)^−/+ or SST-Rac1(CA)^−/+ mice were available for this study. b Representative images from the hippocampal CA1 region, anterior cingulate cortex (ACC), and medial prefrontal cortex (mPFC), in which PV or SST neurons were indicated by red signals. Rac1(CA) signals (green, immunostaining of GFP) were co-localized with PV or SST neurons in all these areas. c Experimental design for social memory using three-chamber sociability and social memory test, for which we designed the inter-trial intervals (ITIs) at either 1 or 5 min before trial 3. d, e When ITI was set at1 min, PV-Cre, Rac1-loxp and PV-Rac1(CA)^−/+ mice went through social memory test. Social memory about the experience of stranger 1 (S1) mouse during trial 2 enabled social preference to stranger 2 (S2) mouse as indicated by more sniff time to S2 than to S1 mouse (n = 9/per group; S1 vs S2, ***p_{1, 2} < 0.001, **p = 0.002, Kruskal-Wallis test) and similar social index among the groups (n = 9/per group, F_(2,24) = 0.857, p = 0.437, one-way ANOVA). f, g When ITI was set at 5 min, social preference to S2 mouse as indicated by more sniff time to S2 than to S1 mouse was significant in controls (PV-Cre or Rac1-loxp) but not in PV-Rac1(CA)^−/+ mice (n = 9/per group; F_(5,48) = 4.291, S1 vs S2, **p₁ = 0.003, *p₂ = 0.044, and p = 0.921, one-way ANOVA). Social index was higher in controls than in PV-Rac1(CA)^−/+ mice (n = 9/per group; F_(2,14) = 9.339, *p₁ = 0.01, *p₂ = 0.02, Brown Forsythe ANOVA test), suggesting that constitutive activation of Rac1 in PV neurons caused rapid forgetting of social memory. h, i When ITI was set at 5 min, sniff time showed similar pattern in SST-Cre, Rac1-loxp, and SST-Rac1(CA)^−/+ mice(n = 9/per group; S1 vs S2, **p₁ = 0.004, *p₂ = 0.016, and **p₃ = 0.001, Kruskal-Wallis test) and social index was not different among groups (n = 9/per group; F_(2,24) = 0.211, p = 0.811, one-way ANOVA). All data showed as mean ± s.e.m.