Maternal-induced shifts in allostatic demands: Reproductive experience alters emotional and cognitive biobehavioral responses in rats (Rattus norvegicus)

Abstract

The arrival and subsequent care of offspring require abrupt shifts in biobehavioral responses in mammalian mothers. In the current study, female rats with one reproductive experience [primiparous (PRIM) rats, n = 8] or no reproductive experience [nulliparous (NULL) rats, n = 8] were assessed in a dry land maze to determine both learning acquisition and responses to uncertainty/prediction errors during the probe trial. Additionally, rats were observed in a swim task and an open field arena to assess responsiveness to varied environmental challenges. Results indicated that the PRIM rats investigated more previously baited wells during the probe trial (on-task behavior) whereas the NULL rats exhibited more peripheral-oriented rearing responses (off-task behavior). Further, a nonsignificant trend was observed indicating more dive responses in the PRIM animals. Focusing on endocrine markers, the PRIM animals had higher DHEA/CORT ratios than the NULL animals following the probe trial. Finally, PRIM animals had less hippocampal glucocorticoid receptor immunoreactivity and more hippocampal BDNF immunoreactivity than NULL animals. In sum, behavioral, endocrine and neural markers suggest that PRIM rats exhibit long-lasting modifications to stress responsivity.

Keywords: Allostasis; BDNF; Corticosterone; DHEA; Emotional resilience; Glucocorticoid receptor; Nulliparous; Primiparous.