We have isolated the cDNA for a novel member (P2X6) of the ATP-gated ion channel family. The rat P2X6 nucleotide sequence encodes a 379 amino acid protein that conserves all the structural features of previously cloned P2X receptors, including the two putative transmembrane domains predicted by hydrophobicity plots. In situ hybridization analysis of rat brain sections showed a wide pattern of mRNA expression that is virtually identical to that already described for P2X4. Injection of P2X6 cRNA in Xenopus oocytes did not give rise to ATP-activated channels. Coexpression of P2X6 with P2X4 subunits produced currents which were not discernibly different from those of P2X4 expressed alone.