Time course of neuronal and synaptic plasticity in dorsal cochlear nucleus of guinea pig following chronic kanamycin-induced deafness.
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.
Kong
W J
WJ
Department of Otorhinolaryngology, Union Hospital of Tongji Medical College, Huazhong Science and Technology University, Wuhan, PR China. wjkong888@yahoo.com
Yin
Z D
ZD
Fan
G R
GR
Yang
Y
Y
Huang
X
X
D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects / Q000502:physiology; D003056:Cochlear Nerve / Q000378:metabolism / Q000648:ultrastructure; D017626:Cochlear Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D003638:Deafness / Q000139:chemically induced / Q000503:physiopathology*; D004195:Disease Models, Animal; D006168:Guinea Pigs; D006309:Hearing / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000235:genetics; D007612:Kanamycin / Q000633:toxicity; D009473:Neuronal Plasticity / Q000502:physiology*; D009498:Neurotoxins / Q000633:toxicity; D017729:Presynaptic Terminals / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism; D020127:Recovery of Function / Q000502:physiology*; D013569:Synapses / Q000378:metabolism* / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000502:physiology; D013997:Time Factors; D015854:Up-Regulation / Q000502:physiology
D009498:Neurotoxins; D012333:RNA, Messenger; D007612:Kanamycin; D007334:Insulin-Like Growth Factor I