Cochlear Threshold Assessment using Tone-Derived Action Potentials

Salt, Alec N.; Vora, Arti

doi:10.3109/00206099009072846

Cited by 13 publications

(1 citation statement)

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“…Whole nerve action potential (AP) thresholds were monitored from an Ag/AgCl ball electrode placed on the otic capsule close to the round window membrane. AP thresholds were tracked throughout the experiment using an automated procedure according to procedures detailed in Salt and Vora [10]. For each threshold measure, stimulus level was increased in 10 dB steps until a suprathreshold response was detected, and then decreased in 5 dB steps until the response amplitude fell below the threshold value.…”

Section: Methodsmentioning

confidence: 99%

Regulation of Cochlear Fluids pH: (II) The Role of Bicarbonate

Suzuki¹,

Wakayama²,

Kotani³

2015

TOOTORJ

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Bicarbonate provides the dominant pH buffer of the cochlear fluids. In the present study, perilymph bicarbonate concentration was manipulated during which endocochlear potential, cochlear fluids pH and cochlear sensitivity to sounds were monitored. Perilymphatic perfusion of medium containing elevated HCO 3 -, at higher pH than normal, produced a decrease in endolymph pH. Similarly, perfusion of nominally HCO 3 --free solution, with lower pH than normal, produced an increase in endolymph pH. When pH changes were induced with HEPES-buffered media, endolymphatic and perilymphatic pH changed in the same direction. The observed endolymph pH changes induced by perilymphatic HCO 3 manipulations therefore depend on HCO 3 -, rather than pH changes. These findings can be explained by the generation of localized changes of CO 2 in the cochlear fluids associated with bicarbonate homeostasis. These data demonstrate some key properties of the CO 2 / HCO 3 buffer system and suggest the likely role for carbonic anhydrase in tissues of the lateral wall. In practical terms, the data also suggest that the pH stability of inner ear fluids cannot be adequately maintained when bicarbonate-altered media are perfused, especially when pH buffers other than HCO 3 are used.

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Section: Methodsmentioning

confidence: 99%