The Ontogenesis of Pseudomonopolar Cells in Spiral Ganglion of Cat and Rat

Abstract

The ontogenesis of type II ganglion cells (TII cell) in the spiral ganglion in the cat and in the rat was studied by light microscopy and by electron microscopy. In the cat, typical pseudomonopolar Til cells with light-coloured cytoplasm containing abundant neurofilaments are observed at birth in the basal part of the cochlea. No TII cells are observed in more immature areas such as the third turn. A constant number of TII cells is present and no typical sign of degenerative ganglion cells is observed throughout postnatal development. In the rat, TII cells can be recognized with confidence at the 6th day post partum. It is suggested that TII cells represent a population of normal cells in the spiral ganglion that can be seen late during ontogenesis.