Figure 8.

The neural cotransporter KCC2 is upregulated by a light-controlled mechanism during turtle retinal development. A, Left panel, Light micrograph of a vertical section through the central retina at S25. Cells and processes are revealed with the H&E stain. Horizontal lines demarcate the outer nuclear (ONL) layer. OPL, Outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Middle panel, Fluorescence micrograph revealing the expression of KCC2 in the same retina as in the left panel. KCC2 is almost entirely restricted to the IPL and OPL, although there is some weak expression on cell bodies in the INL. The bandwidth of the labeling is narrower than the IPL itself (left panel). Right panel, Negative control (no primary antibody, NP). B, Same as A but for a PH3 retina. The bandwidth of the labeling is virtually the same as the IPL itself. C, Same as B but for a DR3 retina. The bandwidth of the labeling is narrower than the IPL itself, as in A. D, Developmental changes in IPL thickness. There is a large increase from S25 to S26, followed by a small decrease from S26 to PH3. The IPL is thicker in DR conditions (gray bar) than in matching controls (PH3). E, Developmental changes in the relative proportion of the IPL occupied by KCC2. There is a major increase from S25 to S26. DR leads to weakening of the labeling compared with matching controls (PH3). F, Developmental changes in KCC2 labeling intensity. The intensity decreases from S25 to S26, but then peaks at PH3, while it reaches its minimum at DR3. ^**p < 0.001; ^*p < 0.01 (N-K post test, each column is compared with the preceding one).