Schematic representation illustrating the expression of purinergic receptors in the adult retina and RPE. Cellular expression of P1 (green), P2Y (black) and P2X (blue) purinergic receptor subtypes is shown close to the indicated cell body of the retina cell type. P, Pigmented epithelium cell; R, rod cell; C, cone cell; H, horizontal cell; B, bipolar cell; M, Müller cell; A, amacrine cell; G, ganglion cell. Receptor subtype expression in the synaptic layers and cell processes is described in text (Section 3).