Effects of Naris Closure on the Olfactory Epithelia of Adult Mice

Over the past several years we have been investigating the effects of unilateral naris closure on the olfactory system of adult mice. Unilateral closure creates an experimental situation in which conditions within the open-side nasal cavity are generally harsher than normal, while conditions on the closed side are generally milder. Because rodents are obligatory nasal breathers, unilateral closure forces all respiratory flows to pass through the open side. This exposes the open side to more odors, xenobiotics, dry air, pathogens and particulate matter than the closed side or normal nasal cavities. In addition. naris closure eliminates the nasal cycle (a pattern of alternating airflow between the two sides of the nose; see Ritter. 1970: Eccles. 1978; Cole and Haight, 1986). We believe that these conditions create a chronic low level of trauma for the open side. while not negatively affecting the closed side. Our studies have examined the effects of unilateral naris closure on: 1) morphology of the olfactory epithelium: 2) rate of mitosis of the neuronal stem cells of the epithelium: and 3) expression of the xenobiotic metabolizing enzyme, cytochrome P-450.