Neuron-like cells on the apical surface of the developing rat olfactory epithelium.

Using scanning electron microscopy (SEM), we encountered a new phenomenon in developing olfactory structures. A few cells with single slender processes that sprout from their cell bodies were found lying on the surface of the developing olfactory epithelium in 15 and 16 day old rat embryos. These slender processes resemble leading processes as they often have filopodia or filopodium-like structures at their distal ends. This finding suggests a presence of a small population of olfactory epithelial cells that resemble, but need not be, neurons. Their location may reflect cell shedding, but the fact that they extend processes over the epithelial surface may also mean that the cells were caught while they were migrating.