Maternal Aggression Driven by the Transient Mobilisation of a Dormant Hormone-Sensitive Circuit

• Aggression - a sexually dimorphic behavior, is prevalent in males and typically absent in virgin females. Following parturition, however, the transient expression of aggression in adult females ensures the pups’ defense from predators and infanticide. While maternal hormones are known to elicit nursing, whether they play a role in the expression of maternal aggression remains unknown. Here we show that a molecularly defined subset of ventral premammillary (PMvDAT) neurons, instrumental for intermale aggression, switch into a hyperexcitable state during lactation. We identify that the maternal hormones prolactin and oxytocin excite these cells, an effect mediated through T-type Ca2+channels. Optogenetic manipulation or genetic ablation of PMvDATneurons profoundly affects maternal aggression, while activation of these neurons impairs the expression of non-aggression-related behaviors. This work identifies a monomorphic neural substrate that incorporates hormonal cues to enable the transient expression of a dormant behavioral program in adult females.Graphical abstractIn BriefMaternal hormones activate a subset of hypothalamic “aggression neurons”, which are required for the transient expression of maternal aggression during lactation.HighlightsQuiescent PMvDATneurons in female mice become hyperexcitable in lactating dams.Manipulation of PMvDATcell activity bidirectionally regulates maternal aggression.The maternal hormones prolactin and oxytocin excite PMvDATcells.Activation of PMvDATneurons impairs the expression of non-aggression-related behavioral programs.

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