Figure 7.

Ipsilaterally and contralaterally projecting tracts co-localise in the ventral funiculus. (A,B) The lipophilic dyes DiI (red) and DiA (green) were injected into contra- and ipsilaterally projecting neurons, respectively. Subsequently, the tissue was cut into 25-μm thick sections. Panel (B) represents the plane of dye injection, and the section shown in (C-E) was 100 μm more rostral relative to (B) (schematic drawing in (A) labels the sections). (C) Post-crossing axons of DiI-labelled dorsal interneurons project in the contralateral ventral funiculus (arrowhead). (D) DiA-labelled ipsilaterally projecting axons are found throughout the ventral funiculus, including the medial part close to the floor plate, where dorsal interneurons turn into the longitudinal axis (arrowhead). (E) An overlay of contra- and ipsilaterally projecting axons shows that these populations co-localize in the ventral funiculus (arrowhead). Note that due to the juxtaposition of the dorsal interneurons and the dorsal funiculus, injection of DiI also stained the longitudinal axonal tracts of the dorsal funiculus (asterisk in (B,C,E)). Ca, caudal; Ro, rostral. Scale bar: 200 μm.