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Extracellular adenosine 5'-triphosphate (ATP) in the endolymphatic compartment influences cochlear function
D J Muñoz1, P R Thorne, G D Housley
1Department of Physiology, University of Auckland, New Zealand.
Hearing Research
|October 1, 1995
Summary
Extracellular adenosine triphosphate (ATP) suppresses cochlear microphonic and endocochlear potential in guinea pigs. This effect, mediated by P2 purinoceptors, suggests ATP plays a role in modulating inner ear function.
Area of Science:
- Neuroscience
- Otolaryngology
- Cellular Physiology
Background:
- P2 purinoceptors are present in cochlear tissues, but the function of extracellular adenosine triphosphate (ATP) in the inner ear remains unclear.
- Previous research indicated ATP presence in cochlear fluids and purinoceptor localization to the endolymphatic compartment, suggesting a localized humoral role.
Purpose of the Study:
- To investigate the influence of extracellular ATP within the endolymphatic space on cochlear function.
- To determine the specific effects of ATP on the cochlear microphonic (CM) and endocochlear potential (EP).
Main Methods:
- ATP (10 microM to 10 mM) in artificial endolymph (EL) was injected into the scala media of guinea-pig cochleae.
- Effects on CM and EP were evaluated using a double-barrelled pipette system for precise volume injection (2-12.5 nl).
- P2 purinoceptor antagonists (suramin, reactive blue 2) were used to block ATP effects.
Main Results:
- ATP demonstrated a significant, dose-dependent suppressive effect on both EP and CM, with a low threshold.
- The observed effects were readily reversible and dose-dependent.
- ATP's effect on EP was specifically blocked by P2 antagonists, while adenosine alone had no impact.
Conclusions:
- This study provides the first evidence of extracellular ATP affecting cochlear function within the endolymphatic compartment via P2 purinoceptors.
- Extracellular ATP appears to play a humoral role in modulating cochlear function, specifically influencing EP and CM.