The term olfactory receptor (OLR) refers to a receptor that is activated by oderant molecules and is located on the apical dendrite of a neuron that mediates the first level of sensory information processing in the olfactory system (OSY) ( Buck-2013 ). The dendrites are embedded in olfactory zones (OLZ), circumscribed areas of olfactory epithelium (OLE) in the mucosal epithelieum that lines the nasal cavity. OLR's have two variants, main olfactory receptor neurons (ORNm) and accessory olfactory receptor neurons (ORNa). The variants are located in different OLZ's within the nasal epithelium, and they respond to different classes of oderant stimuli. Both variants are found in the rats ( Swanson-2004 ) and mouse ( AMBA-2024 ). They are located primarily in the vomeronasal organ (VNO)...though rats have small clusters in several other areas ( Ataffy-2023 ). OLR's differ from most other neurons in the nervous system (NS) in that their lifespan of 30-40 days ( Menini-2003 ) is more similar to that of epithelial cells in other parts of the body than to that of the vast majority of other neurons, which do not replicate during the lifespan of the organism ( Magrassi-2013 ). Final 13 Jan 2025.