Axonal branches and terminations in the cat abducens nucleus of secondary vestibular neurons in the horizontal canal system.

Single vestibular neurons functionally identified as secondary neurons receiving primary afferents from the horizontal canal in the cat were intracellularly stained with horseradish peroxidase (HRP). The vestibular neurons projecting to the ipsilateral abducens nucleus distributed terminal branches in a relatively narrow band in the nucleus. The stem axon of contralaterally projecting vestibular neurons bifurcated into ascending and descending branches in the contralateral medial longitudinal fasciculus. The collaterals emerging from these branches distributed terminals in a relatively wide area in the abducens nucleus. Collateral branches extended into the medial vestibular nucleus, prepositus hypoglossi nucleus and reticular formation.