Nimodipine at a dose that slows ABR latencies does not protect the ear against noise.
We tested the hypothesis that nimodipine, a dihydropyridine reported to increase blood flow, block calcium and potassium channels, and reduce ischemic damage, would alleviate noise-induced hearing loss. Young C57B1/6J mice were exposed to wide-band noise (2 min, 120 dB SPL), with ABR thresholds (4-50 kHz) determined before noise exposure, and from 1 h to 2 weeks afterwards. One group (n = 7) received nimodipine (30 mg/kg/day) in daily peanut butter food supplements beginning 24 h before exposure; the other group (n = 6) received peanut butter alone. In the pretest nimodipine significantly increased the latency of Wave P1 of the ABR (mean difference: 0.16 ms; P < 0.02), showing that calcium blockade depressed sensorineural efficiency, but ABR thresholds were not affected. Noise exposure produced a severe threshold loss that partially recovered in the first week after exposure, and then suffered a slight but significant loss in the second week. These effects were seen equally in both groups: nimodipine did not reduce the severity of the immediate hearing loss following noise exposure, nor did it benefit recovery.
Ison
J R
JR
Department of Brain and Cognitive Sciences, University of Rochester, NY 14627, USA. ison@bcs.rochester.edu
Payman
G H
GH
Palmer
M J
MJ
Walton
J P
JP
D000161:Acoustic Stimulation; D000284:Administration, Oral; D000704:Analysis of Variance; D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects*; D002121:Calcium Channel Blockers / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem / Q000187:drug effects*; D005260:Female; D006317:Hearing Loss, Noise-Induced / Q000188:drug therapy*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009553:Nimodipine / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use*; D011897:Random Allocation
D002121:Calcium Channel Blockers; D009553:Nimodipine