Intranasal oxytocin reduces pre-courtship aggression and increases paternal response in California mice (Peromyscus californicus)

ABSTRACT Oxytocin (OXT) is a neuropeptide that can facilitate prosocial behavior and decrease social stress and anxiety. We investigated whether acute pulses of intranasal (IN) OXT influenced social behavior during social challenges that are likely to occur throughout the lifespan of a wild mouse. To test this, we examined the acute effects of IN OXT in the male California mouse ( Peromyscus californicus ), a monogamous, biparental, and territorial rodent, using a within-subjects longitudinal design. Social challenges included a pre-courtship male-female encounter conducted during the initial aggressive and not the following affiliative phase of courtship, same-sex resident intruder test, and parental care test, with each test and dose separated by at least two weeks. Males were treated with intranasal infusions of 0.8 IU/kg OXT or saline controls 5-min before each behavioral test, receiving a total of three treatments of either IN OXT or saline control. We predicted that IN OXT would 1) decrease aggression and increase affiliation during the pre-courtship aggression phase, 2) increase aggression during resident intruder paradigms and 3) increase paternal care and vocalizations during a paternal care test. As predicted, during pre-courtship aggression with a novel female, IN OXT males displayed less contact aggression than control males, although with no change in affiliative behavior. However, post-pairing, during the resident intruder test, IN OXT males did not differ from control males in contact aggression. During the paternal care test, IN OXT males were quicker to approach their pups than control males but did not differ in vocalizations produced, unlike our previous research demonstrating an effect on vocalizations in females. In summary, during pre-courtship aggression and the paternal care test, IN OXT promoted prosocial approach; however, during the resident intruder test IN OXT did not alter social approach. These data suggest that IN OXT promotes prosocial approach specifically in social contexts that can lead to affiliation. HIGHLIGHTS IN OXT attenuates male aggression during pre-courtship encounters IN OXT does not attenuate male aggression during resident intruder encounters IN OXT increases paternal responsiveness during a paternal care challenge IN OXT in fathers does not influence total paternal care or vocalizations GRAPHICAL ABSTRACT