Effects of daily and acute restraint stress during lactation on maternal aggression and behavior in mice

Abstract

A decreased reactivity to stressors during lactation might heighten the expression of maternal care (including defense of offspring) by minimizing the extent to which stress can impact maternal care. Although stressors applied during pregnancy have variable effects on maternal aggression (or defense of offspring), to date no study has examined the effects of stress applied during the postpartum period on maternal aggression. In this study, we examined the effects of both daily and acute restraint stress (30 min) applied postpartum on maternal aggression and other maternal behaviors. Daily restraint (ending 2 h before testing) did not alter any measure of maternal behavior, including nursing, licking and grooming of pups and pup retrieval, or any measure of maternal aggression. In contrast, acute stress significantly impaired total time aggressive and number of attacks, but pup retrieval was normal. c-Fos levels were significantly elevated in a number of brain regions in association with acute stress, including lateral septum (LS), caudal periaqueductal gray and medial amygdala (MeA), suggesting possible sites where stress reactivity could alter aggression. Together, the results indicate that acute restraint stress impairs maternal aggression and provide a starting point for future studies examining how stress reactivity pathways may intersect with maternal aggression pathways.

Altered maternal profiles in corticotropin-releasing factor receptor 1 deficient mice

“…In other words, the loss of CRFR1 or the use of a CRF receptor antagonist might represent a floor effect whereby further lowering already low levels of CRF neurotransmission does not alter behavior [4]. Recent work suggests that acute stressors applied postpartum also decrease maternal aggression[33]. Given that central release of CRF acting on CRFR1 is an important mediator of the behavioral responses to stress, it would be interesting in future studies to examine whether or how CRFR1-/- and WT mice differ in how postpartum stressors affect maternal aggression.…”

GABA enhancement of maternal defense in mice: Possible neural correlates

“…Another approach to address this issue is to induce stress and examine the effect on aggression. Recent work indicates that with acute restraint, maternal aggression is dramatically reduced (Gammie and Stevenson, 2006). Hence, examining whether CDP could rescue the inhibitory effects of anxiety on aggression could help an understanding of the relationship between fear/anxiety and aggression.…”

GABAA receptor signaling in caudal periaqueductal gray regulates maternal aggression and maternal care in mice

“…Each test day, the same order of behavioral testing was used and because the order of injections was counterbalanced, any carry-over effect would have been equally distributed among groups. It was not expected that performance of the LD test just prior to maternal behaviors would have affected the latter because in previous work we found that application of a strong stressor (restraint) did not affect maternal behaviors [28]. …”

“…Lesions in the caudal (c)PAG increase maternal aggression in rats [51; 52] and injections of serotonin (5-HT) 1 receptor antagonists and 5-HT (2a/2c) receptor agonists into cPAG decrease maternal aggression [14; 15]. Brain activity studies using immediate early genes also indicate an association of cPAG with maternal aggression regulation [25; 26; 28; 34]. Collectively, this evidence suggests that cPAG may play a critical role in the regulation of maternal aggression.…”