Fig. 8.

In situ hybridization of SERT, 5-HT_1B receptor, and VMAT2. Antisense cRNA³⁵S-labeled probes to SERT (B,F, J), the 5-HT_1Breceptor (C, G, K) and VMAT2 (D, H, L) were hybridized to 15-μm-thick coronal sections through the retina at E15 (A–D), P1 (E–H), and P6 (I–L). The retinal pigmented epithelium (pe) was nonspecifically labeled by sense and antisense probes. A, E, andI are bright-field photomicrographs of Nissl-stained sections. A, At E15, two layers can be distinguished in the retina: the undifferentiated neuroepithelial cells and the postmitotic retinal ganglion cell layer (gc). The latter, outlined by a dashed line, first appears close to the optic nerve head (O) and subsequently at the periphery. E, At P1, the ganglion cell layer is clearly separated from the others by the inner plexiform layer.I, By P6, differentiation of the different retinal cell types is complete, and all layers of the retina are distinguishable.B–D, At E15, a small area at the periphery of the retinal ganglion cell (RGC) layer is positive for SERT (B), and a hybridization signal is observed in the entire RGC layer with probes for 5-HT_1B(C) and VMAT2 (D).F–H, At P1, a restricted territory at the periphery of the RGC layer expresses SERT (F), whereas the entire RGC layer is still labeled with 5-HT_1B(G) and VMAT2 (H).J–L, At P6, SERT mRNA labeling has become confined to small patches in the ventral part of the peripheral retina (J). 5-HT_1B expression still extends throughout the RGC layer (K), whereasVMAT2 labeling (L) starts to decrease compared with younger ages. Scale bar: A–D, I–L, 150 μm; E–H, 300 μm.