Auditory and Vestibular Systems, Lateral Line: PDF OnlyDulon Didier; Mollard, Patrice; Aran, Jean-MarieNeuroReport: February 1991 - p 69-72 Buy Abstract 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 $mUM ATP. The application of the structural derivatives ADP and α-β-methyleneATP did not generate significant Ca2+ response. By contrast, ATP-α-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. © Lippincott-Raven Publishers.