ORIGINAL RESEARCH Developmental Shifts in the Behavioral Phenotypes of Inbred Mice: The Role of Postnatal and Juvenile Social Experiences

Abstract The interaction between genotype and environ-ment is an important feature of the process of development. We investigate this interaction by examining the influence of postnatal cross-fostering and post-weaning cross-housing on the behavioral development of 129S and B6 mice. Following cross-fostering, we found significant alterations in the fre-quency of maternal care as a function of maternal strain and pup type as well as interactions between these variables. In adult-hood, we find there are sex-specific and strain-specific altera-tions in anxiety-like behavior as a function of rearing environment, with males exhibiting more pronounced rearing-induced effects. Mixed-strain housing of weanlings was found to lead to alterations in home-cage social and feeding behavior as well as changes in adult anxiety-like responses of 129S mice. Anxiety-like behavior in B6 mice was altered as a function of the interaction between housing condition and weaning weight. These data illustrate the complex pathways through which early and later social experiences may lead to variations in behavior