Influence of prepartum chronic ultramild stress on maternal pup care behavior in mice

Background: Stress administered to pregnant rodents has been shown to lead to biological and behavioral alterations in both mother and pups. Most of t hese stress procedures use noxious stressors. Chronicity is obtained by sim ple repetition of one or two stressors and may be more representative of mo derate daily stress experienced during normal life than stress during sever e life events. The effects of this procedure were assessed by observing mat ernal pup-care behavior and testing maternal aggression. Methods: The subjects included eight controls and eight stressed B6D2F1 fem ales. Chronic ultramild stress was applied from mating to postpartum day (P D) 0. Pup-care behavior was observed on PD 1. Maternal aggression against a male intruder was tested on PD 8, which corresponds to the peak in the dis play of this behavior. Results: Prenatal stress did not affect basic pup-care behavior, but dramat ically impaired defense behavior designed to protect the pups from an exter nal attacker. Conclusions: The results suggest that gestating females subjected to chroni c ultramild stress suffer from a longlasting decline in recognition of exte rnal distress cues either from a resident intruder and/or their own litter. It is assumed these effects are due to the chronicity of the stress rather than its severity. (C) 2000 Society of Biological Psychiatry.