The progesterone receptor and parental behavior in juvenile rats.

Juvenile rats exhibit enhanced parental behavior responses to foster pups from 18 to 25 days of age, compared to virgin adults. Previous studies in adult rats and mice suggest that progesterone can inhibit the display of parental care towards offspring. The present study investigated the role of progesterone in juvenile rat parental behavior. It is hypothesized that the decrease in parental responsiveness as juveniles age is due a progesterone-dependent inhibitory mechanism. Groups of male and female juveniles were subcutaneously implanted with the progesterone antagonist RU486, progesterone, or control implants. All juveniles were then tested for parental behaviors. No significant effects of either RU486 or progesterone treatments on parental behavior latencies were detected in male or female juveniles. The current data support the concept that the mechanisms controlling juvenile and adult parental behavior are divergent. Progesterone does not seem to be involved in the display of parental behavior in juvenile rats.