Evaluation of ?-opioid system functionality in mouse pups: Ultrasonic vocalizations as an index of infant attachment

The evaluation of ultrasonic vocalizations (USVs) during isolation in 6-8-day-old mouse pups can give an indication of the perception of pups' discomfort and need for caretaker presence to overcome the unpleasant condition. Time spent vocalizing changed according to opioid activation, stress exposure, and genetic profile of pups. Deficits in attachment suggest altered opioid functioning and predisposal for long-term defective social behaviors and reward processes.