Assessment of the influence of aging on the olfactory epithelium of rabbits: light and electron microscopic study

ABSTRACT

The present work was carried out to study the olfactory epithelium of rabbits in different ages and to compare age changes in the anterior and posterior areas of the olfactory mucosa. Twelve male Balady rabbits were used and they were divided equally into three age groups, group [1] 3 month old, group [2] 12 month old and group [3] 36 month old. The animals were sacrificed and the olfactory mucosa was peeled from two fixed parts in each group. Part 1 the posterior area of the roof of the nose and Part 2; the anterior upper area of the nasal septum. In group 1, the two examined parts of the olfactory mucosa were similar. The olfactory mucosa was composed of olfactory epithelium resting on a thin basal lamina and lamina propria that was characterized by the presence of Bowman's glands. The olfactory epithelium was composed of olfactory receptor neurons, supporting cells, microvillar cells that occupied the upper and the middle zones of the epithelium and basal cells in the basal zone of the epithelium. In group2, some degenerative changes were encountered in the olfactory epithelium of the two parts, but the anterior part was more affected than the posterior part. In the posterior part, the thickness of the epithelium and the cell population appeared within normal. However, in the anterior part, the thickness of the epithelium and the cell population demonstrated significant decrease. In group3, there were more degenerative changes than those of group 2. The olfactory mucosa from both parts suffered equally from severe degeneration. The most striking feature was replacement of wide areas of the olfactory epithelium with respiratory epithelium. Other areas showed many degenerated cells with significant reduction in the thickness of the epithelium. The presence of Bowman's glands was still characteristic to the olfactory epithelium. From the present study, it could be concluded that the olfactory epithelium was subjected to natural degenerative changes, which increased steadily with age. These changes began firstly in the anterior exposed areas of the epithelium and with the progress of age both areas were equally affected