The nasopalatine ducts of the mouse conserve a functional role in pheromone signaling

Abstract

Social communication in most mammals is mediated by chemosignals, collected by active sniffing and detected mainly by the vomeronasal organ (VNO). In reptiles, however, chemosignals are delivered to the VNO through the oral cavity via the nasopalatine ducts (NPDs) - two direct passageways connecting the nasal and the oral cavities. While the structure of the NPDs is highly conserved across terrestrial vertebrate, it is unclear whether they retain any functional role in mammalian chemosignaling. Here we assess the role of the mouse NPDs in VNO function and associated behavioral responses. By reconstructing the 3D morphological architecture of the mouse snout using micro CT, we identify a net of micro-tunnels forming a direct passageway connecting the NPDs to the nasal cavity and the vomeronasal organ. We further demonstrate that physical obstruction of the NPDs destructs VNO clearance, and reduces chemosignaling-evoked neuronal activation in the medial amygdala. Obstruction of the NPDs also impaired the innate male preference for female chemosignals as well as social approach behavior, indicating the crucial role of the murine nasopalatine ducts in pheromone sensing.