Extracellular ATP elevates cytosolic Ca2+ in cochlear inner hair cells.
The local extracellular application of ATP to isolated sensory inner hair cells (IHC) generated a rapid and transient increase in the concentration of cytosolic free Ca2+, peaking within 1 to 5 s. The dose-response curve indicated a half-max stimulation to be 5 microM ATP. The application of the structural derivatives ADP and alpha-beta-methyleneATP did not generate significant Ca2+ response. By contrast, ATP-alpha-S, an agonist for P2z receptor, was fully active in generating Ca2+ responses. In the absence of extracellular free calcium, the ATP-induced Ca2+ increase was still observed, indicating that ATP generated the liberation of Ca2+ from internal stores. These results suggest that extracellular ATP, through an activation of P2-purinergic receptors, may have a neuromodulatory role in the cochlear physiology at the level of the IHC.
Dulon
D
D
Laboratoire d'Audiologie Expérimentale, INSERM unité 229, Université de Bordeaux II, Hôpital Pellegrin, France.
Mollard
P
P
Aran
J M
JM
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism*; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D005456:Fluorescent Dyes; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000378:metabolism* / Q000502:physiology; D007211:Indoles; D008564:Membrane Potentials; D009994:Osmolar Concentration; D011983:Receptors, Purinergic / Q000378:metabolism; D013050:Spectrometry, Fluorescence / Q000379:methods
D005456:Fluorescent Dyes; D007211:Indoles; D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; C048960:indo-1; D002118:Calcium