The Incisive Duct as a Pathway for Early Vomeronasal Communication in Neonatal Dogs

The detection of chemical signals by the vomeronasal organ (VNO) is critical for communication among mammals from an early age, influencing behaviors such as suckling and recognition of the mother and conspecifics. Located in a concealed position at the base of the nasal cavity, the VNO features a duct covered with a sensory epithelium rich in neuroreceptors. A critical aspect of VNO functionality is the efficient access of stimuli from the nasal and oral cavities to the receptors. In adult dogs, it has been demonstrated through in vivo magnetic resonance imaging and anatomically postmortem how the VNO duct (VD) communicates to the environment through the incisive duct (ID). However, in newborn puppies, the existence of functional communication between the ID and the VD has not been confirmed to date, raising doubts about the potential physiological obliteration of the ID due to its small size and the degree of immaturity of the puppies at birth. Determining this aspect is necessary to evaluate the role played by chemical communication in this critical phase for the survival and socialization of puppies. This study employs serial histological staining techniques to examine the presence and functionality of the incisive duct in neonatal dogs. The serial histological sections have confirmed both the existence of functional communication between both the vomeronasal and incisive ducts in perinatal puppies, and the dual functional communication of the incisive duct with the oral and nasal cavities. The ID shows an uninterrupted lumen along its path and is associated with a sophisticated cartilaginous complex that prevents its collapse, as well as erectile tissue rich in blood vessels and connective tissue that acts as a cushion, facilitating its action under pressure induced by sampling behaviors such as tonguing. This investigation demonstrates the communicative capabilities of the VNO during the perinatal stage in dogs.