Horizontal electron micrographs through PC somata. A, P7. B, P9. C, P12. D, P15. E, P20. PCs are pseudocolored in blue, BDA-labeled CFs are in brown (also indicated by arrows), and BF terminals are in green (asterisks). Boxed regions in A–E are enlarged in Figure 5A–E, respectively. Scale bars: 5 μm.