The effect of unilateral naris occlusion on cell dynamics in the developing rat olfactory epithelium

Abstract

The effect of unilateral naris occlusion on the cellular dynamics of developing olfactory epithelium was investigated in postnatal rats. Nares of rat pups, at 1, 5, and 10 d postnatally, were cauterized; after a 30 d survival period, the olfactory mucosa was examined histologically, and quantitative estimates were made of total number of receptor neurons (together with basal cells), supporting cells, and epithelial thickness. In each group, there were significant differences between occluded and patent sides in total numbers of neurons and in epithelial thickness but no difference in number of supporting cells. The differences were greater in the animals that had been occluded for 1-30 d than in the 5-35 or 10-40 d groups, suggesting that the earlier postnatal days are more sensitive to the effects of occlusion. We evaluated the number of mature olfactory neurons by staining immunohistochemically with an antibody against olfactory marker protein. There were no differences in the number of mature receptor neurons between the occluded and non-occluded sides, indicating the effect of naris occlusion was on the neurons in the immature and/or the 'almost mature' population. Using 3H-thymidine autoradiography, we determined that there was a 40% reduction in the rate of neurogenesis in the animals occluded 1-30 d after birth. Further, the rate of cell proliferation in nasal respiratory epithelium declined by approximately the same amount. The results suggest that the changes in olfactory cell dynamics are probably the result of protective effect of naris occlusion, i.e., the prevention of infectious or toxic agents from entering the occluded side of the nasal cavity, rather than a change in the functional activity of olfactory receptor cells.