Effects of brief stress exposure during early postnatal development in balb/CByJ mice: I. Behavioral characterization.

Early life stress has been linked to the etiology of mental health disorders. Rodent models of neonatal maternal separation stress frequently have been used to explore the long-term effects of early stress on changes in affective and cognitive behaviors. However, most current paradigms risk metabolic deprivation, due to prolonged periods of pup removal from the dam. We have developed a new paradigm in Balb/CByJ mice, that combines very brief periods of maternal separation with temperature stress to avoid the confound of nutritional deficiencies. We have also included a within-litter control group of pups that are not removed from the dam. The present experiments provide an initial behavioral characterization of this new model. We show that neonatally stressed mice display increased anxiety and aggression along with increased locomotion but decreased exploratory behavior. In contrast, littermate controls show increased exploration of novelty, compared to age-matched, colony-reared controls. Behavioral changes in our briefly stressed mice substantially concur with the existing literature, except that we were unable to observe any cognitive deficits in our paradigm. However, we show that within litter control pups also sustain behavioral changes suggesting complex and long-lasting interactions between different environmental factors in early postnatal life.