Fig. 3. Intracellular labeling of the ascending efferent neurons (AEN) of the DON. (A–E) Unstained cross sections through the middle portion of the DON developed for neurobiotin staining. (A) A low-power micrograph capturing the entire DON. The molecular layer appeared as a homogenous tissue lightly stained in brownish color. The principal cell layer appeared as a granular tissue with occasionally spherical structures. This difference forms a clear-cut border between the two compartments of the DON. (B) An enlarged view of the area outlined in A, focusing on the labeled cell. (C–E) Several examples of labeled neurons. The presume axon in C is marked with an arrow. Note that the overall orientations of the cells are along the medio-lateral axis. All of them emit a rather extensive dendritic tree that bifurcates dorsally into the molecular layer and ventrally into the DONs principal cell layer. Scale bar, 100 µm. D, dorsal; V, ventral; L, lateral; M, medial; R, rostral; C, caudal.