From Receptors to Behavior: Molecular and Functional Logic of Sensory Coding in the Mouse Accessory Olfactory System

The accessory olfactory system is specialized for detecting chemical cues that elicit innate reproductive, social, and defensive behaviors and physiological responses in mammals. In mice, vomeronasal sensory neurons express three receptor families, type 1 vomeronasal receptors, type 2 vomeronasal receptors, and vomeronasal formyl peptide receptors, that collectively detect diverse semiochemicals, including pheromones, microbe-derived peptides, and predator cues. Recent advances in molecular organization, structural diversity, and ligand specificity have begun to clarify how vomeronasal receptor families encode ethologically relevant chemical signals, thereby providing initial insight into organizational principles of vomeronasal signaling, including labeled-line and integrative coding strategies. Nevertheless, the vast majority of vomeronasal receptors remain functionally uncharacterized, and the molecular logic of sensory coding in this system is still only partially understood. This review synthesizes current knowledge of vomeronasal receptor diversity, ligand recognition, and accessory mechanisms, while highlighting both the progress made and the major gaps that remain in understanding how receptor-derived signals are transformed into adaptive behavioral and physiological responses.