The origin of efferent vestibular fibres in the guinea pig. A horseradish peroxidase study.

The origin of efferent vestibular neurons was determined in the guinea pig by means of retrograde axonal transport of horseradish peroxidase. After injection of a horseradish peroxidase solution into the ampulla of the horizontal and anterior semicircular canal, efferent vestibular neurons labelled by the granular reaction product were found in the medulla oblongata bilaterally at two locations. The first is lateral to the genu of the facial nerve. It has a bilateral and symmetric origin. The second is the nucleus reticularis pontis caudalis. Here there were more labelled neurons contralateral to the injection site.