Oxytocin and vasopressin enhance responsiveness to infant stimuli in adult marmosets

The neuropeptides oxytocin (OT) and arginine-vasopressin (AVP) have been implicated in modulating sex-specific responses to offspring in a variety of uniparental and biparental rodent species. Despite the large body of research in rodents, the effects of these hormones in biparental primates are less understood. Marmoset monkeys (Callithrix jacchus) belong to a clade of primates with a high incidence of biparental care and also synthesize a structurally distinct variant of OT (proline instead of leucine at the 8th amino acid position; Pro8-OT). We examined the roles of the OT and AVP systems in the control of responses to infant stimuli in marmoset monkeys. We administered neuropeptide receptor agonists and antagonists to male and female marmosets, and then exposed them to visual and auditory infant-related and control stimuli. Intranasal Pro8-OT decreased latencies to respond to infant stimuli in males, and intranasal AVP decreased latencies to respond to infant stimuli in females. Our study is the first to demonstrate that Pro8-OT and AVP alter responsiveness to infant stimuli in a biparental New World monkey. Across species, the effects of OT and AVP on parental behavior appear to vary by species-typical caregiving responsibilities in males and females. •Male marmosets exposed to intranasal Pro8-OT responded to infant stimuli faster than when treated with saline.•Female marmosets exposed to intranasal vasopressin responded to infant stimuli faster than when treated with saline.•OT and AVP did not affect anxiety-like behaviors, indicating that they affect parental behavior specifically in marmosets.•The effects of OT and AVP may depend on species-typical differences in parental behavior rather than on sex alone.