Postpartum scarcity-adversity increases adverse caregiving in the absence of basal corticosterone elevation

Maternal behavior is disturbed by exposure to environmental adversity, including resource scarcity, which can impair maternal care and increase adverse caregiving behaviors like abuse and maltreatment. In rats, exposure to resource scarcity disrupts mother-infant interactions and results in adverse pup-directed maternal behaviors. These changes in maternal behavior are thought to be due to hyperactivity within the hypothalamic-pituitary-adrenal (HPA)-axis, which mediates the stress response. In accordance, upregulation of HPA-axis function is sufficient to drive changes in maternal behavior in rodents. Based on these data, we hypothesized that scarcity-adversity induced changes in maternal behavior would be associated with HPA-axis hyperactivity, as indexed by elevated basal levels of the stress hormone corticosterone (CORT) in rat dams. To test this, we employed a scarcity-adversity paradigm based on creating an impoverished cage environment during postpartum days (PD) 2-9 and examined effects on naturalistic maternal behaviors and basal fecal boli CORT levels (PD 3, PD 5, PD 7) or basal and stress-induced serum CORT levels (PD 9). Surprisingly, rat dams exposed to scarcity-adversity exhibited increases in adverse pup-directed behaviors (e.g., stepping, dragging, shoving) but no elevations in basal or stress-induced CORT levels at any of the time-points assessed. These findings suggest that scarcity-adversity can increase adverse caregiving in a CORT-independent manner. Thus, increases in basal CORT levels are not necessary to induce aberrant maternal behavior in the scarcity-adversity paradigm.