Here we describe a novel purinergic receptor, the P2X5 receptor, cloned from rat heart. The full-length cDNA encodes a protein 455 amino acids long which shares an overall identity of 40-47% with other members of the P2X purinergic receptor family. P2X5 mRNA transcripts are found predominantly in rat heart but are also present in brain, spinal cord and adrenal gland. Functional expression of the recombinant receptor in HEK-293 cells shows a current that resembles mostly the P2X2 phenotype: the ATP-activated current reveals little agonist desensitization, is not activated by alpha,beta-meATP and is completely blocked by suramin and PPADS.