The origin of centrifugal fibers to the inner ear in Caiman crocodilus. A horseradish peroxidase study.

The origin of acoustic and vestibular efferent fibers was investigated in Caiman crocodilus. After injection of horseradish peroxidase (HRP) into the cochlear duct or into the ampullae of the horizontal and anterior semi-circular canals, cells in the medulla oblongata exhibited retrogradely transported HRP reaction product. Efferent vestibular fibers were found in the medial reticular nucleus, at the level of the oliva superior. There were more labeled neurons ipsilateral to the injection site. Efferent acoustic neurons were found close to or inside the rostroventral division of the oliva superior. They spread out into the medial reticular nucleus bilaterally, More labeled efferent acoustic neurons occurred contralateral to the injection site.