To explore the role of nerve growth factor receptor p75NTR during the terminal neuronal development of the mammalian cochlea the onset of hearing and the in vitro response of spiral ganglion neurites to neurotrophin 3 (NT-3), which is known to play a critical role during neonatal inner ear development, were investigated in p75NTR-deficient mice (p75NTR–/–). Auditory-evoked brain stem response recordings from p75NTR–/– and wild-type (WT) littermates were measured from postnatal days (PD) 8 to 23. Additionally, spiral ganglion explants from p75NTR–/– and WT animals were dissected and cultured in an organotypic tissue culture system. In both groups, spiral ganglion neurite outgrowth was analyzed with and without NT-3 supplementation. No significant differences in the onset of hearing of mutant mice compared to the WT mice were detected, and both groups showed a similar development of hearing until PD 23. After stimulation with NT-3, neurite outgrowth was enhanced in both p75NTR–/– and WT mice. However, neurites from p75NTR–/– spiral ganglion explants were longer in both culture conditions. Moreover, NT-3 did not significantly enhance neurite number in p75NTR–/–, as it did in WT mice. P75NTR has a remarkable influence on spiral ganglion neurite growth behavior. However, p75NTR does not seem to be essential for the development of basic hearing function in the first 3 postnatal weeks.

Keywords:
Hearing development, Spiral ganglion, p75NTR, Neurotrophin 3, Inner ear
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2008
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