PERIPHERIN-LIKE IMMUNOREACTIVITY IN TYPE-II SPIRAL GANGLION-CELL BODYAND PROJECTIONS

Peripherin, an intermediate filament protein, is present in neuronal s ubpopulations of both peripheral and central nervous systems. The dist ribution of peripherin was studied in the adult rat cochlea using immu nohistochemistry on whole mount material, in cryostat sections and sec tions of plastic embedded tissue. In the spiral ganglion, peripherin l abeling was restricted to the perikarya of a subpopulation of neurons and their peripheral and central processes. Peripherin positive neuron s had the following features: (i) they have a large eccentric nucleus, they were often found in a cluster of 2 or 3 cells, (ii) they were of ten located near the intraganglionic spiral bundle fibers, (iii) they represented roughly 8% of the whole ganglion population and (iv) on th e average they had smaller perikarya than non-immunoreactive cells. Im munostaining on semithin plastic sections revealed positive reactivity on Type II ganglion cells, while Type I neurons were negative. Double labeling using peripherin and three neurofilament (NF) subunit antibo dies confirmed the presence of both markers within the same spiral gan glion cell type. Type II neurons have been previously documented as th e only subpopulation of the spiral ganglion that presents a strong pos itive NF immunoreactivity within their perikarya. In the organ of Cort i, peripherin-positive fibers formed bundles that course beneath the o uter hair cells and send branches that end as boutons contacting the o uter hair cells. All these characteristics suggest that peripherin-pos itive cells are Type II neurons, and that peripherin constitutes a rel iable marker for this spiral ganglion subpopulation, as well as their peripheral and central processes. (C) 1998 Elsevier Science B.V. All r ights reserved.