Inhibition of L-Type Calcium Channels for Preventing Noise Induced Hearing Loss and Tinnitus

Details

• Personal Author:
  Apawu A ; Hali M ; Holt A ; Muca A ; Wattoo A
• Description:
  Background: Increased spontaneous neuronal activity is thought to underlie the pathological changes in tinnitus. Previous studies have demonstrated efficacy of nimodipine, an L-type calcium channel blocker, on reversing these changes in salicylate and quinine induced tinnitus in rat models (Jastreboff, 1991). However, human trials with nimodipine have not consistently demonstrated efficacy as treatment for tinnitus, prompting examination of other calcium channel blockers. In this study, we examined verapamil as a preventative therapy for noise induced tinnitus and hearing loss. Methods: Male Sprague-Dawley rats (n = 5 - 7/group) were administered verapamil i.p. 15 minutes before a one hour unilateral noise exposure (16 kHz, 106 dB SPL). Hearing thresholds at 12 and 20 kHz were measured using auditory brainstem response (ABR). Gap inhibition of the acoustic startle response (GiASR) was used to assess tinnitus across six frequencies (4, 8, 12, 16, 20 and 24 kHz) at two intensities (45 and 60 dB SPL). Results: There were no significant differences in hearing thresholds between verapamil and saline groups at any time point or frequency. Within an hour following noise exposure, rats administered verapamil demonstrated enhanced Gap detection at both 45 dB (11.5%, p < 0.01) and 60 dB (12.8%, p < 0.05, n = 7/group). The effects were more pronounced 24 hours after noise exposure, with rats that received verapamil suppressing their total startle by 18.0% and 20.2% more than controls at 45 dB and 60 dB, respectively (p < 0.01, n = 7/ group). By five days after noise exposure, rats that received verapamil returned to baseline levels of Gap detection. Conclusions: Our results demonstrate that verapamil may prevent development of noise induced tinnitus and thus warrants further study. Future studies aim to examine the localization of L-type calcium channels in the central auditory system and explore effects of direct verapamil administration. We also plan to examine whether systemic administration of verapamil prevents synapse loss in the cochlea. [Description provided by NIOSH]
• Subjects:
  Animals Biopharmaceutics Hearing Hearing Loss Noise Noise, Occupational Occupational Health Safety
• Keywords:
  Animal Studies Auditory System Ear Disorders Hearing Loss Prevention Hearing Threshold Neurological System Noise Exposure Pharmaceuticals Physiological Effects Tinnitus
• ISSN:
  0742-3152
• Publisher:
  Association for Research in Otolaryngology
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  California ; Michigan ; OSHA Region 5 ; OSHA Region 9
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  39
• NIOSHTIC Number:
  nn:20060978
• Citation:
  Abstr Midwinter Res Meet Assoc Res Otolaryngol 2016 Feb; 39:419
• Federal Fiscal Year:
  2016
• Performing Organization:
  University of Michigan, Ann Arbor
• Peer Reviewed:
  False
• Start Date:
  20050701
• Source Full Name:
  Abstracts of the 39th Midwinter Research Meeting of the Association for Research in Otolaryngology, Febuary 20-24, 2016, San Diego, California
• End Date:
  20280630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:2292478881834c52c1a0365252fdf9c931751db3a199551847f080f054523f8726d79f87678868d0a36c7feea8d759df671bfba0cbb60edaa7c74a1a0b7dd003
• Download URL:
  https://stacks.cdc.gov/view/cdc/224694/cdc_224694_DS1.pdf
• File Type:
  [PDF - 827.86 KB ]