Interaction of a calcium channel blocker with noise in cochlear function in guinea pig.
CONCLUSIONS
Both nifedipine and noise exposure had damaging effects on cochlear function. These damaging effects were subtractive rather than additive, suggesting that calcium channel blockers may have a protective role in noise-induced hearing loss.


OBJECTIVE
We assessed the interaction of nifedipine, a calcium channel blocker, with noise in cochlear function by evaluating changes in the compound action potential (CAP) threshold after the administration of nifedipine with or without noise exposure.


METHODS
Eighty guinea pigs were randomly assigned to eight groups based on those with cochlear perfusion with nifedipine only (0, 0.15, 0.5, and 3 µM, groups 1-4) and noise exposure (groups 5-8). CAP thresholds were recorded using a round window electrode before and 120 min after cochlear perfusion.


RESULTS
Cochlear perfusion of different concentrations of nifedipine caused 2.5, 5.5, 28, and 21.5 dB SPL threshold shift, respectively, at 0, 0.15, 0.5, and 3 µM concentrations (groups 1-4). In comparison, the CAP thresholds after nifedipine perfusion with noise exposure were 43.5, 46.5, 20, and 21.5 dB SPL, respectively, in groups 5-8.
Department of Otolaryngology Head and Neck Surgery, Institute of Otolaryngology, Chinese PLA General Hospital, Beijing, PR China.
Jun
J
Liu
Yu-Guang
YG
Niu
Wan-Xin
WX
Li
Yong-Yi
YY
Yuan
Wei-Ju
WJ
Han
Ning
N
Yu
Shi-Ming
SM
Yang
Xing-Qi
XQ
Li
D000818:Animals; D002121:Calcium Channel Blockers / Q000008:administration & dosage*; D003051:Cochlea / Q000187:drug effects*; D004353:Drug Evaluation, Preclinical; D006168:Guinea Pigs; D006317:Hearing Loss, Noise-Induced / Q000517:prevention & control*; D008297:Male; D009543:Nifedipine / Q000008:administration & dosage*; D009622:Noise / Q000009:adverse effects; D010477:Perfusion
D002121:Calcium Channel Blockers; D009543:Nifedipine