Subsets of retinal neurons and glia express P2Y1 receptors

Recent evidence suggests that extracellular ATP modulates retinal processing and could play a role in modulating glial cells during retinal diseases. Here, we evaluated the localization of P2Y₁ receptors in the rat retina using indirect immunofluorescence immunocytochemistry. We observed labeling within defined populations of inner retinal neurons and Müller cell processes and end feet. Double labeling of P2Y₁ receptor with choline acetyltransferase revealed extensive colocalization indicating the expression of this receptor by cholinergic amacrine cells. Ganglion cell labeling for P2Y₁ receptors was also observed. Having established the normal pattern of immunolabeling within the retina, we next examined whether immunolabeling was altered by retinal disease. P2Y₁ receptor immunolabeling of Müller cells was of greater intensity following light-induced retinal degeneration, suggesting that Müller cell gliosis is accompanied by changes in P2Y₁ receptor expression. Overall, these data provide further evidence for a role of extracellular ATP in retinal signaling within subsets of retinal neurons as well as glia.