Photomicrographs of FR and BDA labeling in transverse sections through the pontine nuclei. A-F, D44; G-I, D45; J-L, D46. The left column (A, D, G, J) shows FR labeling in sections viewed by fluorescence microscopy, the middle column (B, E, H, K) shows BDA labeling in the same sections viewed by conventional light microscopy, and the right column (C, F, I, L) shows an overlay of the two images. A-C show partly overlapping clusters of FR (A) and BDA (B) fibers located slightly rostral to the midpontine level. D-F, show elongated, partially overlapping FR (D) and BDA (E) clusters along the ventral aspect of the peduncle. Compared with the FR labeling, the BDA labeling is slightly shifted towards dorsal, and is, thus, considered to be located more 'externally'. G-I show partly overlapping FR (G) and BDA (K) clusters located close to the midline at a midpontine level. J-L show closely associated curved FR (J) and BDA (K) labeled clusters located laterally in the pontine nuclei. The clusters are incomplete parts of a lamellar subspace. The FR labeling is shifted slightly towards dorsal and lateral, and surrounds the BDA labeling externally. Bar 50 (m (for A-I), and 100 (m (for J-L), D, dorsal; M, medial; mid, midline; ped, peduncle; pn, pontine nuclei; tfp, transverse fibers pons.