Infant rodents are completely dependent on their mothers for survival during their first few weeks of life. Dams provide their offspring with warmth, food, and help void them of waste via anogenital licking. In addition, the first two weeks of life comprise the stress hyporesponsive period during which time rodent pups display blunted stress responses if their mother is present (Levine, 1994). Therefore, experiencing periods of separation from the mother is a salient postnatal stressor that elicits long-term effects on the HPA axis. For example, daily maternal separation for the first 10 days of life resulted in increased expression and reduced DNA methylation of Pomc, a precursor to the hormone ACTH that is released by the pituitary during HPA axis activation (Wu et al., 2014). Daily separation for 360 minutes daily for the first three weeks of life also resulted in reduced Pomc expression in the hypothalamus, while increased expression of Dnmt1 was observed in the pituitary (Todkar et al., 2015). Within the paraventricular nucleus (PVN), adult animals subjected to maternal separation showed hypomethylation and increased expression of arginine vasopressin
