Beschreibung:
<jats:p>We report here the cloning of a chicken cDNA (402 aa) showing high sequence similarity to the previously cloned rat and human P2X<jats:sub>5</jats:sub> receptors (67 and 69%, respectively). The chicken P2X<jats:sub>5</jats:sub> subunit is encoded by a gene composed of 12 translated exons, which shows conserved genomic structure with mammalian <jats:italic>P2X</jats:italic> genes. In HEK‐293 cells heterologously expressing chicken P2X<jats:sub>5</jats:sub> receptors, ATP activates a current that desensitizes in a way that is dependent on the presence of extracellular divalent cations. ATP and 2‐methylthio ATP are equipotent agonists (EC<jats:sub>50</jats:sub> ∼ 2 µ<jats:sc>m</jats:sc>) and suramin and pyridoxal 5‐phosphate‐6‐azophenyl‐2′,4′‐disulfonic acid are potent antagonists. Additionally, reversal potential measurements indicate that chicken P2X<jats:sub>5</jats:sub> is permeable not only to cations but also to chloride (P<jats:sub>Cs+</jats:sub>/P<jats:sub>Cl‐</jats:sub> ∼ 1.9), as has been described for native P2X receptor mediated responses in embryonic chicken skeletal muscle. mRNA distribution of chicken P2X<jats:sub>5</jats:sub> was determined by <jats:italic>in situ</jats:italic> hybridization analysis in both whole embryos and on tissue slices of heart and skeletal muscle. Our results suggest that chicken P2X<jats:sub>5</jats:sub> receptors are expressed in developing muscle and might play a role in early muscle differentiation.</jats:p>