Expression of the P2X2 receptor subunit of the ATP-gated ion channel in the retina.

The site of extracellular ATP signalling in the retina was investigated by examining expression of the P2X2 receptor (P2X2R) subunit which assembles to form ATP-gated ion channels. Indirect in situ RT-PCR in situ hybridization localized the presence of mRNA for the P2X2R subunit within the soma of photoreceptors, inner nuclear layer neurones and the retina ganglion cells. Use of an antiserum specific for the P2X2R subunit confirmed the expression of the protein by these cells and demonstrated a particularly dense immunolabelling within the inner plexiform layer containing the dendritic processes of the retina ganglion cells. The outer segment of the photoreceptors also exhibited P2X2R-like immunoreactivity. The extensive expression of ATP-gated ion channel protein within the retina suggests that extracellular ATP plays diverse neurohumoral roles in regulation of visual processing and cellular homeostasis.