Vasopressin, gonadal steroids and social recognition.

Rodents exposed for a short amount of time to conspecific juveniles spend less time investigating familiar than unfamiliar juveniles. This is based on the formation of an olfactory image of juveniles, which involves an androgen-dependent vasopressinergic pathway in males, as demonstrated by the ability of the vasopressin receptor antagonist dPTyr(Me)VP to block social recognition in intact male but not in female and castrated rats and mice. The involvement of sexually dimorphic vasopressinergic neurons appears to be dependent on the processing of social olfactory cues by the vomeronasal organ since removal of this organ in male rats mimics the effects of castration. These findings are discussed in relation to the role of vasopressin in learning and memory.