Figure 6.

NE- and 5-HT-containing axon terminals are present throughout the XII nucleus. (A and B) Microscopic images of coronal cross-sections through the XII nucleus on one side. The section in A was immunostained for dopamine-ß-hydroxylase (DBH), which in the XII nucleus labels noradrenergic fibers and terminals (black). The section in B was immunostained for 5-HT fibers and terminals. In both panels, selected XII motoneurons that innervate the tongue also were labeled by retrograde transport from the base of the tongue (brown). Typical of motoneurons innervating the genioglossus, most labeled motoneurons are located in the ventromedial quadrant of the XII nucleus. Panels A1 and B1 show enlarged details framed in the corresponding panels on the left. The small dark-brown and black particles in the enlarged images represent fine axonal ramifications and terminals containing NE (in A1) and 5-HT (in B1). NE terminals are especially numerous in the ventromedial portion of the XII nucleus. CE, central canal. (Unpublished data from the study described in Ref. 443.)