Fig. 5. The cholinergic neurons express the P2X₇ receptors and accumulate ATP in granules, which suggests that they could be sources of e-ATP. (A) In the neonatal rat retina the cholinergic cells (red) express the P2X₇ receptors (green), as do many retinal ganglion cells. Confocal image of a P4 retinal section. (B-D) Quinacrine, which labels high levels of ATP stored in granules, is found in the cholinergic cells. (B) Confocal image of a P8 rat cholinergic neuron labeled with Alexa Fluor 568 dextran. (C) A higher magnification of the same cell shows that its soma (red) contains quinacrine labeling (green), which is also shown in isolation in D. Scale bar: 20 µm (A); 40 µm (B); 10 µm (C,D).