Multipolar Neurons In The Spiral Ganglion Of The Rat

Light- and electronmicroscopical studies of the rat spiral ganglion demonstrate that small neurons which are filamentous, thinly encapsulated and contain sparse rough endoplasmic reticulum are consistently present at all ages from weanling to sexually mature. These cells are further characterized by eccentricity of the nucleus, and by the presence of dense-cored vesicles (1200-1400 Å in diameter) scattered in the vicinity of the Golgi complex, in the cytoplasm, or in the cell processes. These neurons comprise about 74% of the ganglion cells and correspond to the unmyelinated neurons described for other species. By use of serial sections, the cells have been determined to be multipolar. Ultrastructurally, they resemble known parasympathetic neurons. Thus, it is suggested that the small, unmyelinated spiral ganglion cells are autonomic (parasympathetic) neurons.