Spiral ganglion neuron loss following organ of Corti loss: a quantitative study.
The packing density of spiral ganglion neurons was measured in 2.5- and 13-15-month-old guinea pigs, in guinea pigs at various times after drug-deafening or acoustic trauma, and in Waltzing guinea pigs of various ages. Analysis of variance and Duncan's new multiple range tests were used to determine significant differences between treatment/survival groups. Spiral ganglion neurons in young and old normal ears did not have significantly different packing densities. Drug-deaf guinea pigs showed a significant loss of neurons by 2 weeks following treatment, a further significant loss by 2 months, and a marginally significant loss between 4 and 8 months. The neuronal population was then stable through 15 months, at about 13% of normal. Acoustic trauma ears showed the first significant loss isn the lower second turn at 1 month. Long-term (12-14 months post-exposure) trauma ears were highly variable. Waltzers lost about 50% of their normal neuronal population between 4 and 8 months; they showed an unexpected greater-than-normal density at 2 months, possible explanations of which are discussed. Thus, loss of the organ of Corti from various causes results in a slow but progressive loss of spiral ganglion neurons, the time course of which varies with the type of cochlear insult.
D000818:Animals; D001306:Auditory Pathways / Q000166:cytology; D002452:Cell Count; D003051:Cochlea / Q000166:cytology*; D004976:Ethacrynic Acid / Q000633:toxicity; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000166:cytology; D006317:Hearing Loss, Noise-Induced / Q000473:pathology; D007612:Kanamycin / Q000633:toxicity; D009474:Neurons / Q000166:cytology; D009925:Organ of Corti / Q000166:cytology* / Q000187:drug effects; D013136:Spiral Ganglion / Q000166:cytology* / Q000187:drug effects
D007612:Kanamycin; D004976:Ethacrynic Acid