Differential effect of the DBA1 and C57BL10 Y chromosomes on the response to social or other stimuli for offense.

Offense was measured in a homogeneous set test and a standard opponent test for two congenic strains of mice. The two congenic strains were DBA1Bg and DBA1.C57BL10Y-Bg, which differ in the Y chromosome. DBA1 males were more aggressive than DBA.C57BL10-Y meles in the homogeneous set test, whereas DBA1.C57BL10-Y males were more aggressive than DBA1 males in the standard opponent test. These findings are consistent with the hypothesis that this Y-chromosomal variant affects an individual's response to social or other stimuli for offense rather than its display of social or other stimuli for offense or its fighting propensity per se. It may be that this is a differential response to urinary chemo-signals.