Early rearing experience is related to altered aggression and vasopressin production following chronic social isolation in the prairie vole

• We examine the relationship between early experience and social stress responses.
• Behavior and HPA responses to social stress were sex- and early care-dependent.
• Low-contact male offspring displayed increased aggression toward a novel conspecific.
• High-contact female offspring had elevated CORT and AVP-ir after long-term isolation.

Parent–offspring interactions early in life can permanently shape the developmental path of those offspring. Manipulation of maternal care has long been used to alter the early-life environment of infants and impacts their later social behavior, aggression, and physiology. More recently, naturally occurring variation in maternal licking and grooming behavior has been shown to result in differences in social behavior and stress physiology in adult offspring. We have developed a model of natural variation in biparental care in the prairie vole (Microtus ochrogaster) and have demonstrated an association between the amount of early care received and later social behavior. In this study, we investigate the relationship between early life care and later aggression and neuroendocrine responses following chronic social isolation. Male and female offspring were reared by their high-contact (HC) or low-contact (LC) parents, then housed for 4 weeks post-weaning in social isolation. After 4 weeks, half of these offspring underwent an intrasexual aggression test. Brains and plasma were collected to measure corticotropin-releasing hormone (CRH) and vasopressin (AVP) immunoreactivity and plasma corticosterone (CORT). Male offspring of LC parents engaged in more aggressive behavior in the intrasexual aggression test compared to HC males. Female offspring of HC parents had higher plasma CORT levels after chronic social isolation and increases in the number and density of AVP-immunopositive cells in the supraoptic nucleus following an intrasexual aggression test. These findings show that the impact of early life biparental care on behavior and HPA activity following a social stressor is both sex-dependent and early experience-specific.