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The effect of loop diuretics upon summating potentials in the guinea pig
Hearing Research
|January 1, 1985
Summary
Ototoxic diuretics ethacrynic acid and furosemide significantly alter inner ear potentials in guinea pigs. Summating potentials (SPs) showed unique changes, indicating potential damage to hair cells.
Area of Science:
- Oto-neuroscience
- Pharmacology
- Auditory Physiology
Background:
- Ototoxic diuretics like ethacrynic acid and furosemide are known to cause hearing loss.
- The precise mechanisms underlying diuretic-induced ototoxicity are not fully understood.
- Electrophysiological changes in the inner ear provide insights into drug effects.
Purpose of the Study:
- To investigate the effects of ethacrynic acid and furosemide on inner ear potentials in guinea pigs.
- To compare the electrophysiological responses to these two ototoxic diuretics.
- To elucidate the impact of these diuretics on cochlear microphonics (CM), summating potentials (SPs), and endocochlear potential (EP).
Main Methods:
- Intravenous administration of ethacrynic acid (50 mg/kg) and furosemide (80 mg/kg) to guinea pigs.
- Recording of cochlear microphonics (CM), summating potentials (SPs), and endocochlear potential (EP) using microelectrodes in scala media.
- Analysis of electrophysiological changes over time post-injection.
Main Results:
- CM and EP changes showed similar patterns: initial decrease followed by a slower increase with ethacrynic acid.
- SPs exhibited distinct changes, including initial high positive values, polarity reversal, and sustained negative potentials.
- Recovery of SPs to normal levels was faster with furosemide (approx. 90 min) than with ethacrynic acid (abnormal even after 140 min).
Conclusions:
- Diuretic-induced ototoxicity differentially affects various inner ear potentials.
- Summating potential alterations suggest a significant impact on inner and outer hair cell function.
- These findings contribute to understanding the ototoxic mechanisms of ethacrynic acid and furosemide.
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