Sensory detection of volatile pup-derived molecules by the mouse vomeronasal organ

Newborns release volatile molecules that are detected by the olfactory system of adult mice triggering pup-directed behaviors, such as parental care or infanticide of unfamiliar pups. However, specific pup-derived pheromones and the sensory neurons in the olfactory system that detect them remain poorly characterized. Here we used a combination of calcium imaging and immunodetection of immediate early genes in vomeronasal sensory neurons to investigate the response to volatile mouse pup-pheromone candidates identified by mass spectrometry. Both ex-vivo calcium imaging and in vivo exposure revealed activation of vomeronasal neurons by combinations of volatile pup-derived molecules. We further characterized the sensory responses using a knockout mouse line deficient for sensory detection in apical vomeronasal neurons. Next, we used a behavioral approach to study the response of adult virgin males and females, as well as fathers and mothers to combinations of pup pheromone candidates painted on dummy newborns. We observed that he presence of these molecules on dummy newborns was capable of promoting typical pup-directed behaviors in the adult mice. Together, these results provide evidence of the involvement of vomeronasal neurons in the detection of volatile pup pheromone candidates identified by mass-spectrometry.