Exposure to early life stress is a predictor of mental health disorders, and two common forms of early life stress are social conflict and impaired maternal care, which are predominant features of postpartum mood disorders. Exposure of lactating female rats to a novel male intruder involves robust social conflict and induces deficits in maternal care towards the F1 offspring. This exposure is an early life social stressor for female F1 pups that induces inefficient lactation associated with central changes in oxytocin (OXT), prolactin (PRL), and arginine vasopressin (AVP) gene expression in adult F1 females.
The mothers of the rats in the current study were either allowed to raise their pups without exposure to a social stressor (control), or presented with a novel male intruder for 1 h each day on lactation days 2–16 (chronic social stress). The effects of this early life chronic social stress (CSS) exposure on subsequent peripheral endocrinology, maternal behavior, and physiology were assessed.
Exposure of female pups to early life CSS resulted in persistent alterations in maternal endocrinology at the end of lactation (attenuated prolactin and elevated corticosterone), depressed maternal care and aggression, increased restlessness and anxiety-related behavior, impaired lactation, and decreased saccharin preference. The endocrine and behavioral data indicate that early life CSS has long-term effects which are similar to changes seen in clinical populations of depressed mothers and provide support for the use of the chronic social stress paradigm as an ethologically relevant rodent model for maternal disorders such as postpartum depression and anxiety.