The Effect of Ammonia on Olfactory Epithelium and Vomeronasal Organ Neuroepithelium of Rabbits

In recent studies, the vomeronasal organ (VNO), although vestigial and with unknown function in humans, was reported to be present in almost every person examined. In rabbits, it is a well-developed organ, one lying on each side of the nasal septum. Histologically it was found to contain neuroepithelium which is considered an accessory olfactory system taking charge of an olfactory discrimination different from that of olfactory epithelium. Experimental removal of the VNO in male animals reduces reproductive performance and aggression. In this study, the effects of prolonged exposure to ammonia vapor on the histological pattern and enzymatic activity of the olfactory epithelium and the VNO neuroepithelium of 30 adult male rabbits were investigated and compared with a control group. In the exposed animals, the supporting cells in both types of epithelia showed hyperplasia which was more marked in the olfactory epithelium. Manifestations of cytotoxicity were found more in the bipolar cells of the olfactory epithelium than in the VNO neuroepithelium. The enzymatic activity in the exposed group supported the histological results. The presence of the VNO neuroepithelium of the rabbit in a narrow duct with a minute nasal orifice could have some protective effects on the cells.