Distinct neuronal populations mediate parenting and infanticide in the amygdalohippocampal area

Abstract Male animals exhibit positive and negative infant-directed behaviors, yet the underlying neural mechanisms remain unknown. The amygdalohippocampal area (AHi) regulates social behavior through neural projections to multiple brain regions. Although AHi neurons that project to the medial preoptic area (MPOA) were reported to promote infanticide in male mice, MPOA-projecting AHi neurons are activated by both parenting and infanticide, suggesting heterogeneity within these neurons. Here using a newly developed, virus-mediated projection-specific and activity-dependent cell labeling method (vPAL), we uncovered two distinct functional, electrophysiological, and transcriptional populations in MPOA-projecting AHi neurons, designated infanticide-related and parenting-related neurons. Furthermore, activation of serotonin receptor 7, which is highly expressed in parenting neurons, selectively suppressed infanticide while promoting parenting in virgin male mice. This study provides a better understanding of the neuronal populations, functions, and properties that previous labeling methods masked.