EXPRESSION OF THE P2X(2) RECEPTOR SUBUNIT OF THE ATP-GATED ION-CHANNEL IN THE RETINA

THE site of extracellular ATP signalling in the retina was investigate d by examining expression of the P2X(2) receptor (P2X(2)R) subunit whi ch assembles to form ATP-gated ion channels. Indirect in situ RT-PCR i n situ hybridization localized the presence of mRNA for the P2X(2)R su bunit within the soma of photoreceptors, inner nuclear layer neurones and the retina ganglion cells. Use of an antiserum specific for the P2 X(2)R subunit confirmed the expression of the protein by these cells a nd demonstrated a particularly dense immunolabelling within the inner plexiform layer containing the dendritic processes of the retina gangl ion cells. The outer segment of the photoreceptors also exhibited P2X( 2)R-like immunoreactivity. The extensive expression of ATP-gated ion c hannel protein within the retina suggests that extracellular ATP plays diverse neurohumoral roles in regulation of visual processing and cel lular homeostasis.