Metabotropic P2Y receptors inhibit P2X3receptor‐channels via G protein‐dependent facilitation of their desensitization

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Abstract
Background and purpose: The aim of the present study was to investigate whether the endogenous metabotropic P2Y receptors modulate ionotropic P2X3receptor‐channels.Experimental approach: Whole‐cell patch‐clamp experiments were carried out on HEK293 cells permanently transfected with human P2X3receptors (HEK293‐hP2X3cells) and rat dorsal root ganglion (DRG) neurons.Key results: In both cell types, the P2Y1,12,13receptor agonist, ADP‐β‐S, inhibited P2X3currents evoked by the selective agonist, α,β‐methylene ATP (α,β‐meATP). This inhibition could be markedly counteracted by replacing in the pipette solution the usual GTP with GDP‐β‐S, a procedure known to block all G protein heterotrimers. P2X3currents evoked by ATP, activating both P2Y and P2X receptors, caused a smaller peak amplitude and desensitized faster than those currents evoked by the selective P2X3receptor agonist α,β‐meATP. In the presence of intracellular GDP‐β‐S, ATP‐ and α,β‐meATP‐induced currents were identical. Recovery from P2X3receptor desensitization induced by repetitive ATP application was slower than the recovery from α,β‐meATP‐induced desensitization. When G proteins were blocked by intracellular GDP‐β‐S, the recovery from the ATP‐ and α,β‐meATP‐induced desensitization were of comparable speed.Conclusions and Implications: Our results suggest that the activation of P2Y receptors G protein‐dependently facilitates the desensitization of P2X3receptors and suppresses the recovery from the desensitized state. Hence, the concomitant stimulation of P2X3and P2Y receptors of DRG neurons by ATP may result both in an algesic effect and a partly counterbalancing analgesic activity.British Journal of Pharmacology(2007)151, 226–236. doi:10.1038/sj.bjp.0707217