The role of lactogenic hormones in maternal behavior in female rats.

Most mammals display an immediate onset of maternal care towards their offspring at parturition. In contrast, inexperienced, nulliparous females are often slow responders and show less intensity in their maternal responses. The transition from a slow responder in non-parous females to a rapid response at parturition is facilitated by the endocrine state of pregnancy. The present report reviews recent evidence from my laboratory demonstrating a role for prolactin in the stimulation of maternal behavior in the rat and presents new findings suggesting tht the conceptus, through its secretion of placental lactogens, helps prime the maternal brain (one site being the medial preoptic area) to respond maternally at parturition.