Brief daily postpartum separations from the litter alter dam response to psychostimulants and to stress

Abstract

Neonatal handling induces several behavioral and neurochemical alterations in pups, including decreased responses to stress and reduced fear in new environments. However, there are few reports in the literature concerning the behavioral effects of this neonatal intervention on the dams during the postpartum period. Therefore, the aim of the current study was to determine if brief postpartum separation from pups has a persistent impact on the dam's stress response and behavior. Litters were divided into two neonatal groups: 1) non-handled and 2) handled [10 min/day, from postnatal day (PND) 1 to 10]. Weaning occurred at PND 21 when behavioral tasks started to be applied to the dams, including sweet food ingestion (PND 21), forced swimming test (PND 28), and locomotor response to a psychostimulant (PND 28). On postpartum day 40, plasma was collected at baseline for leptin assays and after 1 h of restraint for corticosterone assay. Regarding sweet food consumption, behavior during the forced swimming test or plasma leptin levels did not differ between dams briefly separated and non-separated from their pups during the postpartum period. On the other hand, both increased locomotion in response to diethylpropion and increased corticosterone secretion in response to acute stress were detected in dams briefly separated from their pups during the first 10 postnatal days. Taken together, these findings suggest that brief, repeated separations from the pups during the neonatal period persistently impact the behavior and induce signs of dopaminergic sensitization in the dam.

Rat dams exposed repeatedly to a daily brief separation from the pups exhibit increased maternal behavior, decreased anxiety and altered levels of receptors for estrogens (ERα, ERβ), oxytocin and serotonin (5-HT1A) in their brain

“…Furthermore, the stressful properties of the daily repeated brief separation from the pups, as employed herein, is corroborated by the work of Silveira et al (2013). Notably, it has been proposed that the stress of separation of the mother from the pups acts as the trigger to increase maternal behavior (Smotherman, 1983).…”

Chronic psychosocial stress during pregnancy affects maternal behavior and neuroendocrine function and modulates hypothalamic CRH and nuclear steroid receptor expression

“…Importantly, we hypothesize brief periods of pup separation during neuroendocrine and behavioral assays in our study did not significantly contribute to our stress paradigm. Previous studies have shown brief pup separation is not a sufficient stressor to increase maternal HPA axis activity or result in depressive-like behaviors during midto-late lactation 27,[70][71][72][73] . Nevertheless, future studies are needed to determine the precise effect of pup removal on early postpartum neuroendocrine activity and behavior.…”

The stress concept in gastroenterology: from Selye to today

“…Neonatal maternal separation also changes neurocognitive functions 50 and stress responsiveness in the dams 51 ; whether visceral sensitivity of the mothers is altered remains unknown. When pregnant rats are exposed to a gut-sensitizing stimulus, their offspring will also show visceral hypersensitivity 52 .…”