Exposure to early life social complexity shapes vasopressin and galanin neural expression in the communal spiny mouse

Abstract

Early life social experiences shape the development of neural and behavioral phenotypes that persist into adulthood. Although prior research in rodents has demonstrated that early life isolation induces a variety of behavioral deficits, less work has assessed how increased social complexity during early life influences the neuroendocrine mechanisms of social behavior. The spiny mouse (Acomys dimidiatus) is ideal for examining the impact of rearing on offspring neurodevelopment. Spiny mice exhibit communal rearing in the wild, and thus young are exposed to non-kin during early life. Because spiny mice are precocial, they are able to engage in more dynamic social interactions early in life compared to altricial species, potentially enhancing the influences of early life social experiences on the development of the brain. Here we manipulated early life social complexity by rearing spiny mouse pups from birth to weaning with or without non-kin exposure. Once subjects reached adulthood, we collected brains and immunohistochemically labeled neural tissue to assess variation in expression of neurochemicals known to mediate multiple dimensions of social behavior: vasopressin, oxytocin, galanin, and dopamine. Although we observed no influence of rearing condition on oxytocin or dopamine cell numbers, we found that adult vasopressin cell numbers in the anterior hypothalamus were significantly lower and galanin fiber densities in the lateral hypothalamus were significantly higher in animals raised with non-kin. Given vasopressin's role in regulating aggression and galanin's role in modulating anxiety-like behavior, early life non-kin exposure may shape spiny mouse neurodevelopment in a way that facilitates communal living in adulthood.

Keywords: Dopamine; Galanin; Hypothalamus; Oxytocin; Spiny mouse; Vasopressin.