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P2X receptor-mediated changes in cochlear potentials arising from exogenous adenosine 5'-triphosphate in endolymph
D J Muñoz1, P R Thorne, G D Housley
1Department of Physiology, Faculty of Medical and Health Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand.
Hearing Research
|November 27, 1999
Summary
Extracellular adenosine 5'-triphosphate (ATP) suppresses cochlear function via P2 receptors. This study identifies P2 receptors as ATP-gated ion channels mediating these effects in guinea pig cochlear fluids.
Area of Science:
- Oto-neuroscience
- Molecular Pharmacology
Background:
- Extracellular adenosine 5 -triphosphate (ATP) is present in cochlear fluids.
- Previous studies demonstrated ATP's dose-dependent suppressive effect on endocochlear potential (EP) and cochlear microphonic (CM) via P2 receptors.
Purpose of the Study:
- To characterize the specific P2 receptor subtypes involved in mediating ATP's suppressive effects on cochlear function.
- To investigate the role of P2 receptor agonists and antagonists in modulating ATP-induced changes in EP and CM.
Main Methods:
- Microinjection of ATP, P2 receptor agonists, and antagonists into the scala media of guinea pig cochlea.
- Monitoring of EP and CM in response to these microinjections.
- Comparison of ATP effects across different cochlear turns (first vs. third).
Main Results:
- ATP and P2 receptor agonists significantly suppressed EP and CM.
- Neither adenosine nor uridine 5 -triphosphate, nor P2 receptor antagonists alone, affected EP and CM.
- The suppressive effect of ATP was more pronounced in the third cochlear turn compared to the first.
Conclusions:
- Extracellular ATP in the endolymphatic compartment influences cochlear function through P2 receptors.
- These P2 receptors likely function as ATP-gated ion channels.
- The findings contribute to understanding the role of purinergic signaling in auditory physiology.
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