Peripherin as a marker for degeneration of spiral ganglion neurons after aminoglycoside ototoxicity

Abstract

Conclusion. Our data show that temporary appearance of atypical type 1 neurons, like type 3 neurons, might be another degenerating form of spiral ganglion neurons (SGNs); peripherin might be a marker of degenerating neurons. Objectives. Further morphological and biochemical studies on surviving SGNs after loss of hair cells might offer clues for preventing their degeneration. Materials and methods. We observed the ultrastructural features of surviving SGNs and analyzed the peripherin immunoreactivity at 4, 10, or 20 weeks after systemic injection of neomycin in rats. Results. Type 3 neurons, similar to type 1 neurons but unmyelinated, appeared in the spiral ganglion by 4-week survival, and showed a survival advantage in remaining SGNs by longer surviving periods. We observed neurons packed with dense intermediate filament and with multiple layers of dense myelin sheath (atypical type 1 neurons) in the degenerating neurons. Atypical type 1 neurons were observed among the degenerating neurons in the 4- and 10-week survival groups, but disappeared in longer surviving animals. By means of immunohistochemistry, only smaller SGNs of normal rats were strongly stained by anti-peripherin antibody, whereas increased immunoreactivity was observed in both large and small remaining neurons after neomycin treatment, especially in 10- and 20-week survival animals.

• Intermediate filament
• inner ear
• neomycin
• immunohistochemistry
• TEM