Distribution of motor and internuclear neurons in abducens nucleus of the cat

The abducens nucleus is said to contain at least two types of neurons, ie, the motor neurons which supply the ipsilateral lateral rectus muscle, and the internuclear neurons which project to the medial rectus subdivision of the oculomotor complex via the contralateral medial longitudinal fasciculus. The distribution pattern of the motor and internuclear neurons within the abducens nucleus was examined in the cat, after horseradish peroxidase was injected into the lateral rectus muscle and the oculomotor complex, respectively. The results showed that both motor and internuclear neurons are distributed widely and intermingled without any topographical difference throughout the entire length of the abducens nucleus, and that the ratio of the motor to internuclear neurons was approximately 80:20-70:30.