Fig. 4. Cell proliferation test for cell clusters 9 and 10. Number of BrdU+ cells in cluster 9 (A–C) and in cluster 10 (D–F) after 1 (A,D), 7 (B,E) and 14 (C,F) days of social interaction. Values are the sum of labeled cells from the two bilateral cell clusters 9 or 10 of a brain, and expressed as median ± interquartile range. (A,D) After 1 day, the number of BrdU+ cells did not differ for dominant (D), subordinate (S) and isolate (I) animals (Kruskal–Wallis test for overall difference: P_cluster9=0.87; P_cluster10=0.32). (B,E) After 7 days, isolated animals had significantly more BrdU+ cells in cluster 9 than subordinate animals but not more than dominant animals (Kruskal–Wallis test for overall difference: *P<0.05 (P=0.02); multiple comparison tests: P_IvsS<0.05; P_IvsD and P_DvsS >0.05). There was a non-significant trend for the isolates to have more BrdU+ cells in cluster 10 than subordinate and dominant animals (Kruskal–Wallis test for overall difference: P=0.03; multiple comparisons test: P_IvsD is >0.05 and P_IvsS <0.10; P_DvsS>0.10. (C,F) After 14 days, the number of BrdU+ cells did not differ among the groups (Kruskal–Wallis test for overall difference: P_cluster9=0.64; P_cluster10=0.91). (Numbers in parentheses indicate the number of animals examined.)