Distal pup cues attenuate defensive reactivity and fear-potentiated startle magnitude in postpartum rats without altering sensorimotor gating.

Using a novel behavioral paradigm that integrates fear-potentiated startle (FPS) and prepulse inhibition testing, this study examined how motherhood and infant cues impact innate defensive reactivity (as measured by the magnitude of basal startle reflex), attentional processing (as measured by prepulse inhibition), acquisition, and expression of conditioned fear (as measured by the FPS) in postpartum female rats. Sprague-Dawley mother rats from Postpartum Day 3-9 were tested in this paradigm either in the presence or absence of their own two pups (Experiments 1 and 2), and their performance was compared to virgin female rats and males (Experiment 3). Compared to mother rats tested alone, those tested with their pups being placed inside the apparatus (with no physical contact) showed significantly reduced baseline startle response and reduced overall startle magnitude under the FPS testing procedure. Importantly, this pup-induced reduction of baseline startle and fear startle was only observed in mother rats, not in virgin females or male rats. Notably, pup presence did not alter prepulse inhibition under various testing conditions nor did it affect the acquisition and expression of FPS. Also, postpartum females did not differ from virgin females and males in the acquisition and expression of conditioned fear. Together, these results suggest that distal pup cues may powerfully inhibit defensive reactivity in mother rats, without altering aversive learning or sensorimotor gating ability. The possible behavioral mechanisms involved in this pup effect are discussed. (PsycInfo Database Record (c) 2026 APA, all rights reserved).