Facilitation of transmitter release from rat sympathetic neurons via presynaptic P2Y(1) receptors

BACKGROUND AND PURPOSE: P2Y(1), P2Y(2), P2Y(4), P2Y(12) and P2Y(13) receptors for nucleotides have been reported to mediate presynaptic inhibition, but unequivocal evidence for facilitatory presynaptic P2Y receptors is not available. The search for such receptors was the purpose of this study. EXPERIMENTAL APPROACH: In primary cultures of rat superior cervical ganglion neurons and in PC12 cell cultures, currents were recorded via the perforated patch clamp technique, and the release of [(3)H]-noradrenaline was determined. KEY RESULTS: ADP, 2-methylthio-ATP and ATP enhanced stimulation-evoked (3)H overflow from superior cervical ganglion neurons, treated with pertussis toxin to prevent the signalling of inhibitory G proteins. This effect was abolished by P2Y(1) antagonists and by inhibition of phospholipase C, but not by inhibition of protein kinase C or depletion of intracellular Ca(2+) stores. ADP and a specific P2Y(1) agonist caused inhibition of Kv7 channels, and this was prevented by a respective antagonist. In neurons not treated with pertussis toxin, (3)H overflow was also enhanced by a specific P2Y(1) agonist and by ADP, but only when the P2Y(12) receptors were blocked. ADP also enhanced K(+)-evoked (3)H overflow from PC12 cells treated with pertussis toxin, but only in a clone expressing recombinant P2Y(1) receptors. CONCLUSIONS AND IMPLICATIONS: These results demonstrate that presynaptic P2Y(1) receptors mediate facilitation of transmitter release from sympathetic neurons most likely through inhibition of Kv7 channels.