Rodent vomeronasal organ

Mendoza A. (1993). Morphological studies on the rodent main and accessory olfactory systems the regio olfactoria and vomeronasal organ. Anat Anz 175, 425-446. 

As with many macrosmatic mammals, rodents have two separate chemosensory systems, the main olfactory system (MOS) and accessory olfactory system (AOS), which respond to social odors. Importantly, these sensory systems differ not only in their peripheral morphology and central projections, but also in the types of chemosignals that they process (Meredith 1991). Sensory neurons of the MOS, which are located in the main olfactory epithelium and project to the main olfactory bulbs, process volatile chemicals and can detect odors at a distance. In contrast, sensory neurons of the AOS, which are located in the vomeronasal organs (VNO) and project to the accessory olfactory bulbs, primarily process large, non-volatile chemicals and require contact for stimulation (Meredith 1991). 

Table 5.3 Role of the vomeronasal organ in rodent behavior...

Rats ovulate when exposed to soiled bedding from males. The stimulus is nonvolatile, as a wire screen can eliminate this response. Vomeronasal organ occlusion reduces the response, implicating this pathway for priming pheromone reception in this species (Johns etal., 1978). Table 8.2 summarizes the role of the vomeronasal in priming effects in rodents. 

The vomeronasal system, also known as the accessory olfactory system, consists of chemoreceptors, organized into the VNO, the vomeronasal nerve, its terminal, the accessory olfactory bulb, and more central pathways. First described by Jacobson in 1811, the VNO has been studied intensely. We now know how stimuli reach it and what behaviors it mediates. The VNO occurs in amphibians, reptiles, and mammals. Among mammals, it is best developed in marsupials and monotremes. In birds it only appears during embryogenesis. The VNO and its function are best known for squamate reptiles, particularly snakes, and rodents and ungulates among the mammals. 

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