The neural control of infanticide and parental behaviors in male mice

Infanticide, the killing of conspecific young, is a natural behavior observed commonly in non-parental animals across species, including mice. Our recent study in female mice revealed a mutually inhibitory circuit, composed of estrogen receptor alpha cells in the medial preoptic area (MPOA^Esr1) and the posterior part of the bed nucleus of stria terminalis (BNSTp^Esr1), that controls pup-directed behaviors, with the former driving maternal care and the latter promoting infanticide. Given that both MPOA and BNSTp are sexually dimorphic, here we asked whether the same circuit operates in males. Our functional manipulations and in vivo and in vitro recordings reveal that MPOA^Esr1 and BNSTp^Esr1 cells similarly and respectively drive paternal care and infanticide and antagonize each other in male mice. Furthermore, during fatherhood, MPOA^Esr1 cell excitability increases while BNSTp^Esr1 cell excitability decreases to enable the switch from infanticide to paternal care. Despite the similarity in circuit organization, a direct comparison between males and females reveals sex differences in the intrinsic properties of MPOA^Esr1 and BNSTp^Esr1 cells. Thus, MPOA^Esr1-BNSTp^Esr1 emerges as a common circuit motif for controlling pup-directed behaviors in both sexes, whereas the activity balance between these two populations differs between sexes and likely contributes to the different tendencies in males and females to express pup-caring versus killing behaviors.