Coupling of the nucleotide P2Y 4 receptor to neuronal ion channels

G protein‐linked P2Y nucleotide receptors are known commonly to stimulate the phosphoinositide signalling pathway. However, we have previously demonstrated that the cloned P2Y 2 , P2Y 6 and P2Y 1 receptors couple to neuronal N‐type Ca 2+ channels and to M‐type K + channels. Here we investigate the coupling of recombinant, neuronally expressed rat‐ and human P2Y 4 receptors (rP2Y 4 , hP2Y 4 ) to those channels. Rat sympathetic neurones were nuclear‐injected with a P2Y 4 cDNA plasmid. A subsequent activation of rP2Y 4 or hP2Y 4 by UTP (100 μ M ) in whole‐cell (ruptured‐patch) mode produced only about 12% inhibition of the N‐type Ca 2+ current ( I Ca(N) ). Surprisingly, in perforated patch mode, UTP produced much more inhibition of I Ca(N) (maximally 51%), with an IC 50 value of 273 n M . This inhibition was voltage‐dependent and was blocked by co‐expression of the βγ‐binding transducin Gα‐subunit. Pertussis toxin (PTX) pretreatment also suppressed I Ca(N) inhibition. UTP inhibited the M‐current, recorded in perforated patch mode, by (maximally) 52%, with IC 50 values of 21 n M for rP2Y 4 and 28 n M for hP2Y 4 . This inhibition was not affected by PTX pretreatment. With rP2Y 4 , ATP inhibited the M‐current (IC 50 524 n M , 26 times weaker than UTP), whereas ATP had no agonist activity at hP2Y 4 . This suggests a difference in agonist binding site between rP2Y 4 and hP2Y 4 . We conclude that, in contrast to other nucleotide receptors studied, the P2Y 4 receptor couples much more effectively to M‐type K + channels than to Ca 2+ channels. Coupling to the Ca 2+ channels involves the βγ‐subunits of G i/o ‐proteins and requires a diffusible intracellular component that is lost in ruptured‐patch recording.British Journal of Pharmacology (2003) 138 , 400–406. doi: 10.1038/sj.bjp.0705043