[Neuroanatomical distribution of motor and internuclear neurons within the cat abducens nucleus demonstrated by a...

The abducens nucleus contains two types of neurons which are motor and internuclear neurons. The neuroanatomical control system and the distributions of these two neurons were studied by simultaneous retrograde labeling with two different tracer substances in the cat. The tracers were Fluoro-Gold (FG) and wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP). The types of cells were clearly identified by separate injections of FG or WGA-HRP into the right lateral rectus muscle and the left medial rectus muscle. The motor neurons labeled with FG were intermingled among the neurons which were labeled with WGA-HRP. No double-labeled neuron was detected within the abducens nucleus. These results indicate that motor and internuclear neurons in the abducens nucleus have their own projections and no neuron has dual projections.