Prenatal stress suppresses rat pup ultrasonic vocalization and myoclonic twitching in response to separation.

Prenatally stressed infant rats were separated from their dams and littermates on postnatal Day 14 and their rates of ultrasonic vocalizations (USVs) and myoclonic twitching in response to that separation were recorded. Compared to control pups, prenatally stressed pups vocalized significantly less often and showed significantly less myoclonic twitching in response to this test. Results are interpreted in terms of the ability of prenatal stress to produce infants that are behaviorally inhibited when in a novel or stressful situation.