Anxiety profiles of mice selectively bred for intermale aggression

In the present study we compared genetically selected aggressive (TA) and nonaggressive (TNA) male mice, as well as males from an unselected control line (SW), in three tests of anxiety: the elevated plus-maze, the light-dark box, and the staircase test. Males were tested repeatedly for 3 days. In all three tests TA males were found to be more active and less anxious than TNA males, with SW males showing more or less intermediate scores. Furthermore, repeated plus-maze testing induced anxiety-like behavior in both TA and TNA mice, whereas repeated testing in the light-dark and staircase paradigms resulted in different responses. Whereas TNA animals were found to be stable, TA animals showed habituation on the second and third day of testing. The obtained data support the conclusion that a higher-level offensive aggression entails lower level of anxiety.