Differentiation of the Olfactory Epithelium during Deyelopment

Abstract

Maturation of the olfactory epithelium was studied in the rat. As a deyelopmental index of the olfactory epithelium, quantitation was based on the thickness and the number of cell layers of the epithelium. Mean epithelial thicknesses were 84 μm on embryonic day (E) 19, 94 μ m on postnatal day (P) 0. 98 μ m on PIO and 57 μ m in adult. Ayerage numbers of cell layers were 7 (E19). 8 (P0). 10 (P10) and 7 (adult). Thus the olfactory epithelium progressiyely increased in thickness between P0 P10, and later decreased in thickness as well as in number of cell layers toward adult. To clarify the number of mature receptor cells sending their axons to the olfactory bulb, the percentages of receptor cell labeling (number of labeled cells total number of receptor cells) were estimated with an aid of retrograde fluorescent tracer injected into the olfactory bulb. As a result, their percentages were 34% (PI P3). 50% (P8 P10) and 78% (adult). The ablation experiment of the bulb on PI pups and adult rats reyealed that the percentages of receptor cell degeneration were 31% in neonates (PI) and 76% in adults, confirming the results obtained from the retrograde tracing. Thus the present study shows the substantial increase of mature receptor cells during deyelopment and may proyide a morphological basis in understanding of the functional maturity of olfaction.

Key Words:

• olfaetory receptor cells
• maturity
• fluorescent tracer
• degeneration method
• rat