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Tetraethylammonium effects on cochlear potentials in the guinea pig
M G van Emst1, S F Klis, G F Smoorenburg
1Department of Otorhinolaryngology, Utrecht University, The Netherlands.
Hearing Research
|August 1, 1995
Summary
Tetraethylammonium (TEA) blocks potassium (K+) channels in cochlear hair cells, revealing their partial role in generating the summating potential (SP). TEA
Area of Science:
- Neuroscience
- Auditory Physiology
- Otolaryngology
Background:
- Voltage-dependent K+ channels in cochlear hair cells are implicated in non-linear current-voltage relationships.
- These relationships may contribute to the generation of the extracellular summating potential (SP).
Purpose of the Study:
- To evaluate the role of K+ channels in the generation of the SP.
- To investigate the effect of K+ channel blockade on SP generation in the guinea-pig cochlea.
Main Methods:
- Perilymphatic perfusion technique to introduce tetraethylammonium (TEA), a K+ channel blocker.
- Measurement of sound-evoked cochlear potentials (SP) in scala vestibuli and scala tympani.
- Use of tetrodotoxin (TTX), a Na+ channel blocker, to block nerve activity.
Main Results:
- TEA induced reversible negative shifts in SP without blocking nerve activity, suggesting a direct effect on afferent fibers.
- After nerve blockade with TTX, TEA caused a small, reversible decrease in SP magnitude, significant at high frequencies (8-12 kHz).
- TEA did not affect the endocochlear potential.
Conclusions:
- The rapidly activated K+ channel in inner hair cells (IHCs) is likely blocked by TEA, contributing partially to SP generation.
- The asymmetric contribution of this K+ channel to IHC current-voltage relationships is only partly responsible for SP generation.
- K+ channels play a limited, frequency-dependent role in SP generation, with afferent fiber activity being a significant factor.