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http://www.jneurosci.org/content/34/39/13110
.abstract
Postnatal Expression of Neurotrophic Factors
Accessible to Spiral Ganglion Neurons in the
Auditory System of Adult Hearing and
Deafened Rats
1. Erin M. Bailey1 and
2. Steven H. Green1,2
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1. Author contributions: E.M.B. and S.H.G. designed research; E.M.B. performed research;
E.M.B. and S.H.G. analyzed data; E.M.B. and S.H.G. wrote the paper.
1. The Journal of Neuroscience, 24 September 2014, 34(39): 13110-13126; doi:
10.1523/JNEUROSCI.1014-14.2014
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Abstract
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Abstract
Spiral ganglion neurons (SGNs) receive input from cochlear hair cells and project from the
cochlea to the cochlear nucleus. After destruction of hair cells with aminoglycoside antibiotics or
noise, SGNs gradually die. It has been assumed that SGN death is attributable to loss of
neurotrophic factors (NTFs) derived from hair cells or supporting cells in the organ of Corti
(OC). We used quantitative PCR (qPCR) to assay NTF expression—neurotrophin-3 (NT-3),
BDNF, GDNF, neurturin, artemin, and CNTF—in the OC and cochlear nucleus at various ages
from postnatal day 0 (P0) to P90 in control hearing and neonatally deafened rats. NT-3,
neurturin, and CNTF were most abundant in the postnatal hearing OC; CNTF and neurturin most
abundant in the cochlear nucleus. In the OC, NT-3 and CNTF showed a postnatal increase in
expression approximately concomitant with hearing onset. In rats deafened by daily kanamycin
injections (from P8 to P16), surviving inner hair cells were evident at P16 but absent by P19,
with most postsynaptic boutons lost before P16. NT-3 and CNTF, which normally increase
postnatally, had significantly reduced expression in the OC of deafened rats, although CNTF was
expressed throughout the time that SGNs were dying. In contrast, neurturin expression was
constant, unaffected by deafening or by age. CNTF and neurturin expression in the cochlear
nucleus was unaffected by deafening or age. Thus, NTFs other than NT-3 are available to SGNs
even as they are dying after deafening, apparently conflicting with the hypothesis that SGN death
is attributable to lack of NTFs.
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cochlea
deafness
neuronal survival
neurotrophic factor
organ of Corti
spiral ganglion
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Received March 13, 2014.
Revision received July 29, 2014.
Accepted August 18, 2014.
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Copyright © 2014 the authors 0270-6474/14/3413110-17$15.00/0