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Vestibular Evoked Myogenic Potentials Are Heavily Dependent on Type I Hair Cell Activity of the Saccular Macula in Guinea Pigs
- Source :
- Audiology and Neurotology. 14:59-66
- Publication Year :
- 2008
- Publisher :
- S. Karger AG, 2008.
-
Abstract
- This study applied the vestibular evoked myogenic potential (VEMP) test to guinea pigs coupled with electronic microscopic examination to determine whether VEMPs are dependent on type I or II hair cell activity of the saccular macula. An amount of 0.05 ml of gentamicin (40 mg/ml) was injected directly overlaying, but not through, the round window membrane of the left ear in guinea pigs.One week after surgery, auditory brainstem response test revealed normal responses in 12 animals (80%), and elevated thresholds in 3 animals (20%). The VEMP test using click stimulation showed absent responses in all 15 animals (100%). Another 6 gentamicin-treated animals underwent the VEMP test using galvanic stimulation and all 6 also displayed absent responses. Ultrathin sections of the saccular macula in the gentamicin-treated ears displayed morphologic alterations in type I or II hair cells, including shrinkage and/or vacuolization in the cytoplasm, increased electron density of the cytoplasm and nuclear chromatin, and cellular lucency. However, extrusion degeneration was rare and only present in type II hair cells. Quantitative analysis demonstrated that the histological density of intact type I hair cells was 1.1 ± 1.2/4000 μm2 in the gentamicin-treated ears, showing significantly less than that in control ears (4.5 ± 1.8/4000 μm2). However, no significant difference was observed in the densities of intact type II hair cells and supporting cells between treated and control ears. Furthermore, the calyx terminals surrounding the damaged type I hair cells were swollen and disrupted, while the button afferents contacting the damaged type II hair cells were not obviously deformed. Based on the above results, we therefore conclude that VEMPs are heavily dependent on type I hair cell activity of the saccular macula in guinea pigs.
- Subjects :
- Physiology
Vestibular evoked myogenic potential
Guinea Pigs
Stimulation
Vestibular Nerve
Guinea pig
Hair Cells, Vestibular
Speech and Hearing
otorhinolaryngologic diseases
medicine
Animals
Antibacterial agent
Round window
Chemistry
Anatomy
Sensory Systems
Anti-Bacterial Agents
Microscopy, Electron
medicine.anatomical_structure
Acoustic Stimulation
Vestibular Diseases
Otorhinolaryngology
Vacuolization
Evoked Potentials, Auditory
sense organs
Hair cell
Gentamicins
Type II Hair Cell
Subjects
Details
- ISSN :
- 14219700 and 14203030
- Volume :
- 14
- Database :
- OpenAIRE
- Journal :
- Audiology and Neurotology
- Accession number :
- edsair.doi.dedup.....34953421303c086be7caac1f851914b9