Effects of biparental rearing on ultrasonic vocalization (USV) responses of rat pups (Rattus norvegicus).

This study investigated the influence of social rearing on ultrasonic vocalization (USV) responses of 11- to 12-day-old rat (Rattus norvegicus) pups in isolation to the presence or removal of an anesthetized adult. Pups were reared with the dam or dam plus a virgin female (aunt), their biological sire, or a castrated male. All pups reduced rates of USV in contact with anesthetized adults. Pups' USV rates after the adult's removal depended on their rearing experience. After removal of the dam, pups increased USV rates over baseline (potentiation). Pups reared with aunts potentiated USV after contact with adult females but suppressed USV after contact with males. Pups reared with sires potentiated USV after contact with sires or strange males. Pups reared with castrated males did not suppress USV after contact with castrates but did after contact with unfamiliar intact males. Thus, pups' differential USV responses to contact with passive adults in isolation can be acquired during prior rearing experience.