Brain aromatase dynamics reflect parental experience and behaviour in male mice

Abstract

AbstractIn most mammals, providing paternal care is not automatic. In house mice, experience with pups governs the extent and quality of paternal care. First-time fathers undergo a dramatic transition from ignoring or killing pups to caring for pups. The behavioural shift occurs together with changes in brain estrogen signalling as indicated by changes in estrogen receptor presence and distribution in multiple areas regulating olfaction, emotion, and motivation. Here, we report estrogen dynamics by altered local estrogen synthesis via changes in aromatase, a key enzyme catalysing the conversion of testosterone to estrogen. The amount of paternal experience (5 or 27 days) was associated with increased numbers of immunocytochemically-identified aromatase expressing cells in the medial and cortical amygdala, piriform cortex, and ventromedial hypothalamus. In the lateral septum, and to some extent in the medial preoptic area, parental experience increased aromatase only in fathers with 27 days of experience, and only in the right brain hemisphere, a new case of brain-functional lateralisation with experience. Nuclei/areas associated with maternal care (medial preoptic area, bed nucleus of stria terminalis, nucleus accumbens) exhibited a left-hemisphere advantage in aromatase expressing cells. This newly found lateralisation may contribute to the left-hemisphere dominant processing and perception of pup calls to release parental behaviour.