Maternal aggression in rodents: brain oxytocin and vasopressin mediate pup defence

Abstract

The most significant social behaviour of the lactating mother is maternal behaviour, which comprises maternal care and maternal aggression (MA). The latter is a protective behaviour of the mother serving to defend the offspring against a potentially dangerous intruder. The extent to which the mother shows aggressive behaviour depends on extrinsic and intrinsic factors, as we have learned from studies in laboratory rodents. Among the extrinsic factors are the pups' presence and age, as well as the intruders' sex and age. With respect to intrinsic factors, the mothers' innate anxiety and the prosocial brain neuropeptides oxytocin (OXT) and arginine vasopressin (AVP) play important roles. While OXT is well known as a maternal neuropeptide, AVP has only recently been described in this context. The increased activities of these neuropeptides in lactation are the result of remarkable brain adaptations peripartum and are a prerequisite for the mother to become maternal. Consequently, OXT and AVP are significantly involved in mediating the fine-tuned regulation of MA depending on the brain regions. Importantly, both neuropeptides are also modulators of anxiety, which determines the extent of MA. This review provides a detailed overview of the role of OXT and AVP in MA and the link to anxiety.

Keywords: HAB/LAB; central amygdala; intracerebroventricular; paraventricular nucleus; receptor agonist/antagonist.

Figure 1

Proposed model of changes in the intensity of maternal aggression from mid-pregnancy to lactation in the rat. The highest level of maternal aggression occurs in early lactation, i.e. the first week postpartum, and declines afterwards until weaning. Adapted from [23]. © Blackwell Publishing Ltd.