Kir4.1 potassium channel expression in glial cells of the retina. Astrocytes are shown in blue, Müller cells inred, and Kir4.1 channels in green in this triple-labeled confocal fluorescence image of the rat retina. The potassium channel is prominently expressed in Müller cell processes along blood vessels (bottom left) but not in astrocytes. Overlap of Kir4.1 channels and Müller cells is shown in yellow. The black circles are unlabeled ganglion cell somata, which are surrounded by Müller cell processes. Antibodies against glial fibrillary acidic protein (astrocytes), glutamine synthetase (Müller cells), and Kir4.1 were used. For details, see the article by Kofuji et al. in the August 1, 2000 issue (pages 5733–5740).