Figure 4. Apocynin effectively blocks the burst generated in the photoreceptor layer. Retinal explants were treated with either dihydroethidium (DHE)/peanut agglutinin (PNA; A, B, C) or dihydrorhodamine (DHR)/PNA (D, E, F). In some cases, explants were pretreated with 4 mM apocynin for 3 h at 37 °C (C, F). Before imaging, explants were treated with full medium (A, D), basal medium (B, E), or apocynin in basal medium (C, F). Retinal whole mounts were cultured and oriented as described in the Material and Methods. Arrows point to the PNA-stained cones (red) that produce oxidized DHR123 (green). These data were typical of at least three independent experiments. Confocal slices collected were 2.0 μm thick. Representative slices are shown. The scale bar represents 10 μm.