Fig. 1

Acute dCA2 silencing impairs social memory. a AAV-DIO-hM4Di-IRES-mCitrine injection into dCA2 of Amigo2-Cre mice. b Overlap of mCitrine (green) and RGS14 (magenta). c Anterior extent of mCitrine expression. d Action potentials recorded from hM4Di-expressing CA2 PNs (n = 10) in response to progressively higher depolarizing currents before (baseline) and after CNO application. e Rheobase is increased after CNO application (paired t test: t(9) = 2.967, P = 0.0158). f Direct interaction test of social memory performed 30 min after CNO IP in hM4Di-expressing and control (GFP-expressing) Amigo2-Cre mice. g When the same stimulus mouse encountered in trial 1 is also encountered in trial 2, GFP-expressing but not hM4Di-expressing mice showed decreased social exploration time (two-way ANOVA: treatment × trial F(1,17) = 14.85, P = 0.0013; GFP: n = 10, P = 0.0006, Sidak’s multiple comparisons test; hM4Di: n = 9, P = 0.5572, Sidak’s multiple comparisons test). h When a novel stimulus mouse was encountered in trial 2, neither GFP-expressing nor hM4Di-expressing mice showed decreased social exploration (two-way ANOVA: treatment × trial F(1,12) = 0.5303, P = 0.4805; GFP: n = 8, t(7) = 1.078, P = 0.3169, paired t test; hM4Di: n = 6, t(5) = 0.07924, P = 0.9399, paired t test). i Reduction in social exploration time in trial 2 by groups from g and h. For GFP-expressing mice, reduction in exploration during trial 2 to the same (Fam, familiar) mouse presented in trial 1 was significantly greater than reduction when a novel (Nov) mouse was presented in trial 2 (unpaired t test: t(16) = 2.851, P = 0.0116) or when hM4Di-expressing mice encountered a familiar mouse in trial 2 (unpaired t test: t(17) = 3.962, P = 0.0010). No difference was found between GFP and hM4Di-expressing mice encountering a novel mouse in trial 2 (unpaired t test: t(12) = 0.6749, P = 0.5126). Results in e, g and h show mean ± s.e.m. Box-whiskers plot in i present median (center line), 25th to 75th percentiles (box) and minimal and maximal values (whiskers). *P < 0.05; **P < 0.01; ***P < 0.001; ns, P > 0.05. Scale bars, 250 µm (b and c)