Early Social Enrichment Shapes Social Behavior and Nerve Growth Factor and Brain-Derived Neurotrophic Factor Levels in the Adult Mouse Brain

Background: Early experiences produce persistent changes in brain and behavioral function. We investigate whether being reared in a communal nest (CN), a form of early social enrichment that characterizes the natural ecological niche of many rodent species including the mouse, has effects on adult social/aggressive behavior and nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) levels in mice. Methods: The CN consisted of a single nest where three mothers kept their pups together and shared care-giving behavior from birth to weaning (postnatal day 25). Results: Compared to standard laboratory conditions, in CN condition, mouse mothers displayed higher levels of maternal care. At adulthood, CN mice displayed higher propensity to interact socially and achieved more promptly the behavioral profile of either dominant or subordinate male. Furthermore, CN adult mice showed higher NGF levels, which were further affected by social status, and higher BDNF levels in the brain. Conclusions: Our findings indicate that CN, a highly stimulating early social environment, produces differences in social behavior later in life associated with marked changes of neurotrophin levels in selected brain areas, including hippocampus and hypothalamus. © 2006 Society of Biological Psychiatry.