Maternal separation followed by isolation-housing differentially affects prepulse inhibition of the acoustic startle response in C57BL/6 mice.

Exposure to chronic stress is associated with an increased incidence of neuropsychiatric dysfunction. The current study evaluated two competing hypotheses, the cumulative stress and the match/mismatch hypothesis of neuropsychiatric dysfunction, using two paradigms relating to exposure to "stress": pre-weaning maternal separation and post-weaning isolation-housing. C57BL/6 offspring were reared under four conditions: typical animal facility rearing (AFR, control), early handling (EH, daily 15 min separation from dam), maternal separation (MS, daily 4 hr separation from dam), and maternal and peer separation (MPS, daily 4 hr separation from dam and from littermates). After weaning, mice were either housed socially (2-3/cage) or in isolation (1/cage) and then tested for prepulse inhibition in adulthood. Isolation-housed MPS subjects displayed greater deficits in prepulse inhibition relative to socially-housed MPS subjects while socially-housed AFR subjects displayed greater deficits in prepulse inhibition relative to isolation-housed AFR subjects. The results indicate that these treatment conditions represent a potentially valuable model for evaluating the match/mismatch hypothesis in regards to neuropsychiatric dysfunction.

Brief and long periods of maternal separation affect maternal behavior and offspring behavioral development in C57BL/6 mice.

For rats, maternal mediation of brief and longer term dam-pup separations were thought to account for pup differences in adult "emotionality." In this study, early handling (EH), maternal separation (MS), and maternal peer separation (MPS) groups were compared to an animal facility reared (AFR) group for maternal behavior and offspring adult open-field behavior in C57BL/6 mice. Although MS and MPS dams displayed higher levels of maternal behavior upon reunion, these group differences did not predict offspring open-field behavior. However, when offspring behavior was analyzed as a function of specific aspects of maternal behavior, irrespective of treatment group, pups that received high levels of quiescent nursing and activity, but not licking, were less "emotional." Individual differences in maternal licking of pups predicted variability of "emotional" behavior for AFR and EH pups. Thus, for this strain of mouse, individual and not treatment differences in maternal care predict offspring "emotional" development.