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Brain Res. 2010 Apr 30;1328:118-29. doi: 10.1016/j.brainres.2010.01.055. Epub 2010 Jan 29.

Time course of neuronal and synaptic plasticity in dorsal cochlear nucleus of guinea pig following chronic kanamycin-induced deafness.

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Department of Otorhinolaryngology, Union Hospital of Tongji Medical College, Huazhong Science and Technology University, Wuhan, PR China.


We investigated the time course of the plasticity in fusiform cell (FC) and at auditory nerve (AN) synapse on FC (AN/FC synapse) following chronic kanamycin-induced deafness. Guinea pigs were treated with kanamycin sulfate by subcutaneous injection at dose of 500 mg/kg/day for 7 days. Ultrastructural changes in FC and AN/FC synapse were observed, and local insulin-like growth factor 1 (IGF-1) mRNA was quantified using quantitative real time PCR at 1, 7, 14, 28, 70 and 140 days after kanamycin treatment. The average threshold was 46.46+/-3.45, 80.63+/-5.95 and 103.95+/-6.59 dB SPL respectively at 1, 7 and 14 days, and the threshold was statistically unchanged at 28, 70 and 140 days in comparison with the 14 day group. Mitochondrial swelling in FC and at AN/FC synapse was progressive at 7, 14 and 28 days. Moreover, the thickness of the postsynaptic densities increased at 1, 7 and 14 days. Finally, there was a persistent upregulation in local IGF-1 mRNA at 7, 14, 28 and 70 days. These changes in the ultrastructure of AN/FC synapse and FC, and upregulation of local IGF-1 mRNA were no longer present at 140 days. Our results indicate that the effects of kanamycin on the ultrastructure of FC and AN/FC synapse are progressive. However, FC and AN/FC synapse are capable of reviving and remodeling after kanamycin-induced lesion and incomplete deafferentation. Additionally, local IGF-1 might play a role in the lesion- and deafness-induced plasticity in FC and at AN/FC synapse following chronic kanamycin-induced deafness.

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