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Osmotically induced pressure difference in the cochlea and its effect on cochlear potentials
1Department of Otorhinolaryngology, Utrecht University, The Netherlands.
Hearing Research
|May 1, 1994
Summary
Low-frequency sound stimulation and osmotic pressure changes both displace the basilar membrane, altering electrophysiological potentials. These findings support the theory that basilar membrane displacement causes changes seen in endolymphatic hydrops.
Area of Science:
- Oto-neuroscience
- Auditory physiology
- Electrophysiology
Background:
- Electrophysiological effects from scala tympani displacements in low-frequency biasing experiments mirror those in endolymphatic hydrops.
- This suggests basilar membrane displacement underlies endolymphatic hydrops changes.
- A key difference is dynamic displacement in biasing versus static displacement in hydrops.
Purpose of the Study:
- To investigate if static basilar membrane displacement, induced by osmotic pressure changes, affects electrophysiological potentials.
- To compare the effects of dynamic (biasing) and static (osmotic) basilar membrane displacement.
Main Methods:
- Experiments involved perfusing perilymphatic spaces with hypotonic (183 mOsm/kg) and hypertonic (397 mOsm/kg) solutions.
- Electrophysiological recordings included summating potential (SP), compound action potential (CAP) at 4 kHz, and cochlear microphonics.
- Basilar membrane displacement was induced via osmotic pressure manipulation.
Main Results:
- Hypotonic perfusate increased SP and decreased CAP.
- Hypertonic perfusate decreased both SP and CAP.
- Cochlear microphonics remained largely unaffected by osmotic changes.
Conclusions:
- Both dynamic (biasing) and static (osmotic pressure) displacement of the basilar membrane induce similar changes in SP and CAP.
- These findings support the hypothesis that basilar membrane displacement toward the scala tympani is a significant factor in the electrophysiological alterations observed in endolymphatic hydrops.