Comparison of the protective efficacy of neurotrophins and antioxidants for vibration-induced trauma.
BACKGROUND
Patients undergoing temporal bone surgery or subjects working with vibrating tools may develop vibration-induced hearing loss (VHL). The aim of this study was to characterize the effects of pretreatment with N-acetylcysteine (NAC) or the neurotrophic factors, brain-derived neurotrophic factor (BDNF) and ciliary neurotrophic factor (CNTF), on VHL in an animal model.


METHODS
Trauma to the cochlea was created with a vibrating probe placed on the bone of the external ear canal. BDNF and CNTF(Ax1) were delivered into the cochlea with mini-osmotic pumps. NAC was delivered into the cochlea by round window membrane (RWM) injection, by RWM permeation, or by oral administration. Hearing was evaluated with electrocochleography (ECoG).


RESULTS
For control animals, vibration resulted in an average immediate threshold shift of 42 +/- 26 dB. NAC provided no protective benefit in animals subjected to VHL, regardless of the delivery method, with average threshold shifts varying from 38 to 56 dB across groups. NAC injection through the round window membrane was toxic, causing a ECoG threshold shift of >25 dB. In BDNF+CNTF(Ax1)-treated animals, immediate hearing loss was similar to that in control animals. There was a trend of threshold recovery by 1 day after vibration; however, the improvement was not statistically significant, nor was there a significant difference in 1-day thresholds across groups.


CONCLUSIONS
Local infusion of BDNF and CNTF(Ax1) may enhance the rate of recovery from VHL, compared to control animals. In contrast, NAC had no effect on VHL, and when delivered by RWM injection, was actually toxic to the inner ear.
Zou
Jing
J
Department of Otolaryngology, Tampere University Hospital, Teiskontie 35, FI-33521 Tampere, Finland.
Bretlau
Poul
P
Pyykkö
Ilmari
I
Toppila
Esko
E
Olovius
N Petri
NP
Stephanson
Niklas
N
Beck
Olof
O
Miller
Josef M
JM
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001300:Audiometry, Evoked Response; D001309:Auditory Threshold / Q000187:drug effects; D004710:Endolymph / Q000378:metabolism; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000187:drug effects; D006319:Hearing Loss, Sensorineural / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control*; D009414:Nerve Growth Factors / Q000378:metabolism / Q000494:pharmacology*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D014732:Vibration
D000975:Antioxidants; D009414:Nerve Growth Factors; D018696:Neuroprotective Agents