Carbonic anhydrase in the generation of cochlear potentials

Area of Science:

• Physiology
• Neuroscience
• Otolaryngology

Background:

• Hypercapnia, elevated CO2 levels, can impact inner ear function.
• Carbonic anhydrase plays a role in physiological processes, but its specific effect on endocochlear potentials (EP) is not fully understood.

Purpose of the Study:

• To investigate the role of carbonic anhydrase in the generation of endocochlear potentials (EP) during hypercapnia.
• To determine if inhibiting carbonic anhydrase affects EP changes induced by breathing elevated CO2 concentrations.

Main Methods:

• Experiments were conducted on 18 guinea pigs, divided into two groups.
• Hypercapnia was induced by breathing 10% CO2-90% O2. Carbonic anhydrase was inhibited using methazolamide or acetazolamide administered intravenously.
• Endocochlear potentials (EP), endocochlear PO2, and cochlear microphonics (CM) were recorded using microelectrodes and a silver-wire electrode.

Main Results:

• Initial hypercapnia exposure increased EP by approximately +6 mV, while cochlear microphonics (CM) decreased.
• During subsequent hypercapnia with carbonic anhydrase inhibited, the elevation in EP observed initially was prevented.
• These findings suggest carbonic anhydrase is crucial for EP generation under these experimental conditions.

Conclusions:

• Carbonic anhydrase activity is essential for the generation of endocochlear potentials (EP) during hypercapnia.
• Inhibition of carbonic anhydrase blocks the typical EP response to elevated CO2 levels.
• This study provides novel insights into the mechanisms underlying EP regulation in the inner ear.