Neonatal maternal separation alters reward-related ultrasonic vocalizations in rat dams

We examined the effects of brief or long durations of repeated maternal separation (MS) on ultrasonic vocalizations (USVs) in rat dams. 50-kHz USVs putatively identified as maternal in origin were emitted only immediately after pups were returned following MS. Maternal USV emission also depended on separation duration and pup age. Given that 50-kHz USVs are emitted in response to rewarding stimuli, MS may induce duration-dependent effects on maternal positive affect.