Reduction of noise-induced hearing loss using L-NAC and salicylate in the chinchilla.
The effects of a combination of two antioxidant compounds were studied in a chinchilla model of noise-induced hearing loss. After obtaining baseline hearing thresholds using inferior colliculus evoked potentials, chinchillas were exposed for 6 h to octave band noise centered at 4 kHz (105 dB SPL). Post-noise thresholds were obtained 1 h after the noise exposure, and then animals received either saline or salicylate and N-L-acetylcysteine combination. Another group received antioxidant treatment 1 h prior to noise. Hearing was tested at 1, 2 and 3 weeks post-noise. Subsequently, the cochleae were harvested, and cytocochleograms were prepared. There was a 20-40 dB SPL threshold shift at 3 weeks for tested controls. Permanent threshold shifts (PTS) were significantly reduced (P<0.05) to approximately 10 dB for the pre-treatment group at week 3. The PTS for the post-treatment group at week 3 was similar to the pre-treatment group at 1 and 2 kHz (0-10 dB) but was intermediate between the control and pre-treatment groups at 4 and 8 kHz (23 dB). Animals pre-treated with antioxidant had a significant reduction in hair cell loss but those post-treated with antioxidant had no protection from hair cell loss. These findings demonstrate the feasibility of reduction of noise-induced hearing loss using clinically available antioxidant compounds.
Kopke
R D
RD
Department of Defense Spatial Orientation Center, Naval Medical Center San Diego, San Diego, CA 92134-2200, USA. rkopke@nmcsd.med.navy.mil
Weisskopf
P A
PA
Boone
J L
JL
Jackson
R L
RL
Wester
D C
DC
Hoffer
M E
ME
Lambert
D C
DC
Charon
C C
CC
Ding
D L
DL
McBride
D
D
D000111:Acetylcysteine / Q000627:therapeutic use*; D000818:Animals; D001299:Audiometry; D001309:Auditory Threshold / Q000187:drug effects; D002452:Cell Count; D002682:Chinchilla; D004338:Drug Combinations; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000473:pathology; D006317:Hearing Loss, Noise-Induced / Q000188:drug therapy* / Q000503:physiopathology; D012459:Salicylates / Q000627:therapeutic use*
D004338:Drug Combinations; D012459:Salicylates; D000111:Acetylcysteine