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Extracellular ATP elevates cytosolic Ca2+ in cochlear inner hair cells
1Laboratoire d'Audiologie Expérimentale, INSERM unité 229, Université de Bordeaux II, Hôpital Pellegrin, France.
Neuroreport
|February 1, 1991
Summary
Extracellular adenosine triphosphate (ATP) rapidly increases intracellular calcium in auditory inner hair cells (IHCs), suggesting a neuromodulatory role in hearing. This calcium release originates from internal stores, not extracellular influx.
Area of Science:
- Auditory Neuroscience
- Cell Physiology
- Purinergic Signaling
Background:
- Sensory inner hair cells (IHCs) are crucial for auditory transduction.
- The role of extracellular nucleotides in cochlear function is not fully elucidated.
Purpose of the Study:
- To investigate the effect of extracellular adenosine triphosphate (ATP) on intracellular calcium levels in isolated IHCs.
- To determine the mechanism of ATP-induced calcium signaling in IHCs.
Main Methods:
- Isolated rat cochlear inner hair cells were used.
- Extracellular application of ATP and its analogs (ADP, α,β-methyleneATP, ATP-α-S).
- Measurement of cytosolic free Ca2+ concentration using calcium imaging.
Main Results:
- Extracellular ATP application caused a rapid, transient increase in cytosolic free Ca2+ in IHCs (peak 1-5s).
- Half-maximal stimulation occurred at 5 μM ATP; ADP and α,β-methyleneATP were ineffective.
- ATP-α-S, a P2z receptor agonist, elicited a significant Ca2+ response.
- ATP-induced Ca2+ increase persisted in the absence of extracellular calcium, indicating release from internal stores.
Conclusions:
- Extracellular ATP activates P2-purinergic receptors on IHCs.
- ATP triggers the release of intracellular calcium stores.
- Extracellular ATP may play a neuromodulatory role in cochlear physiology at the IHC level.