Fig. 2.

Selective deficits in social behavior in NL-4-KO mice. (A) Social interaction of male mice in pairs of the same genotype (WT, n = 8; NL-4-KO, n = 10) was observed over 10 min in an open arena. Bars represent total time mice spent in contact. (B–D) Evaluation of social interaction of individual WT (n = 19) and NL-4-KO mice (n = 18) in a tripartite arena. (B) Time spent in the compartment with a stranger mouse versus empty compartment. (C) Preference index for stranger, calculated as [time_stranger/(time_stranger + time_empty)]×100–50. (D) Number of visits to the compartment of the stranger. (E and F) Social memory of individual WT (n = 19) and NL-4-KO mice (n = 18) was investigated in a tripartite arena immediately after the social interaction test (B–D). (E) Time spent in the compartment with previously explored stranger vs. new stranger. (F) Preference index for new stranger, calculated as [time_new/(time_new + time_familiar)]×100–50. (G and H) Evaluation of aggression of WT (n = 19) and NL-4-KO mice (n = 17) exposed to an intruder. (G) Attack latency of the resident. (H) Proportion of resident mice exhibiting aggression behavior. Data are presented as mean ± SEM. Asterisks indicate a significant change in NL-4-KO mice (P = 0.0005, A; P = 0.0001, B; P = 0.03, C; P = 0.04, D; P = 0.002, E; P = 0.04, F; P = 0.004, G; P = 0.02, H). (I) Correlation between intruder approach and resident escape behavior in a modified resident-intruder setting [n = 16, WT; n = 28, NL-4-KO; Z = 3.1, P = 0.002 for WT (solid line), n = 28, Z = 0.6, P = 0.6 for NL-4-KO (dashed line) in Spearman correlation analysis].