Meeting Abstract
In mammals, maternal care is universal and its neural bases well-studied, whereas paternal care is much rarer and less well understood. In house mice, paternal care is gained with experience. Naïve males ignore and often kill pups, and only display parental behaviour after several days’ exposure to pups. This delay coincides with altered neuroendocrinology; injection of estrogen helps naïve males become parental and experience with pups increases estrogen receptor content in limbic brain areas. Here, we asked whether locally produced estrogen (via aromatase) may contribute to becoming paternal, by quantifying limbic brain aromatase levels (number of Arom+ cells) in naïve males (M0, no pup contact); fathers co-caring their first litter of pups with a female partner for 5 days (M5, 5 days of pup exposure); and males co-caring with a female partner their first litter of pups until weaning and their second litter of pups for 5 days (M27, 27 days of pup exposure). Only males with previous pup experience retrieved lost pups back into the nest (% males retrieving pups; M0: 0%; M5: 83%; M27: 92%). The number of Arom+ cells increased in M5 and M27 relative to M0 in the lateral septum, amygdala, piriform cortex, and ventromedial hypothalamus. There were, however, no significant changes in nuclei associated with maternal care (medial preoptic area, bed nucleus of the stria terminalis, nucleus accumbens). Our results show increased paternal performance coincides with increased Arom activity in brain areas that regulate emotional/motivational and olfactory signal processing and learning. We suggest local estrogen is involved in a paternal brain network that is different from the network regulating the maternal instinct in females.
