Central oxytocin regulates social familiarity and scent marking behavior that involves amicable odor signals between male mice

The effect of oxytocin on social behavior and odor communication was investigated in male C57BL/6J mice. In three-male colonies, in visible burrow systems, icv oxytocin (OT) infusion before colony formation substantially increased huddling together over the initial 8 h of grouping, accompanied by decreased expression of a number of social approaches associated with conspecific aggression and defense. OT antagonist infusion had little impact on expression of social approaches but decreased time engaging in social components including huddle over the initial 8 h. These results demonstrate a linkage of social familiarity to OT availability in the brain. In a scent marking paradigm central infusion of OT reduced territorial marking towards male conspecifics, and this in turn reduced the scent marking of untreated stimulus males to OT-infused subjects. Infusion of an OT antagonist into stimulus mice who were confronted with OT-infused subjects prevented the reduction/suppression of scent marking that was normally seen following exposure of social odors released from OT-injected mice. Odor of pair-housed mice also induced a suppression of territorial scent marking in odor recipients, but OT antagonist administration into pair-housed mice blocked this suppressive effect of odor cue. These results indicate that central OT modulates release as well as detection of amicable signals facilitating/maintaining familiar relationships and suppressing territorial behavior between male mice. Overall, these findings suggest that OT plays a significant role in regulating social familiarity via changing qualities of conspecific odor cues.