Functional Role of the Incisive Duct in Neonatal Dogs.

Introduction: The detection of chemical signals by the vomeronasal organ (VNO) is critical for mammals from an early age, influencing behaviors such as suckling and recognition of the mother. Located at the base of the nasal cavity, the VNO features a duct covered with a sensory epithelium. 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 how the vomeronasal duct (VD) communicates to the environment through the incisive duct (ID). 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. Determining this aspect is necessary to evaluate the role played by chemocommunication in the survival and socialization of puppies. Methods: This study employs serial histological staining to examine the presence and functionality of the ID in neonatal dogs. Additionally, a histochemical study was conducted using periodic acid-Schiff and Alcian Blue staining, along with labeling with six lectins to characterize the expression of glycoconjugates in the incisive papilla and in the area between the ID and the VD. Results: The histological study has confirmed both the existence of functional communication between both ducts in perinatal puppies and the dual functional communication of the ID with the oral and nasal cavities. Lectin labeling has allowed for the characterization of the glycoconjugate expression profile in the papilla and ID, showing significant differences between lectins. Conclusion: The ID is associated with a sophisticated cartilaginous complex that prevents its collapse, as well as erectile 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. Plain Language Summary: This study examined how newborn puppies use a special structure, the vomeronasal organ (VNO), to detect chemical signals that help them recognize their mother and locate milk. The VNO has a duct connected to the outside through another passage, the incisive duct (ID). While this connection is known in adult dogs, it had not been confirmed in newborns, raising questions about its role in early life. Through detailed tissue analysis, researchers confirmed the presence of this connection in puppies, allowing access to chemical cues from both the nose and mouth. The ID contains structures that keep it open and responsive, along with specific chemicals in the area that may help puppies recognize scents. These findings support the importance of an active VNO for survival and social behavior from birth. [ABSTRACT FROM AUTHOR]