Vestibular Efferent Fibers to Each of the Ampulla of the Anterior, Lateral and Posterior Semicircular Canals in Cats -A Horseradish Peroxidase Study

Abstract

The origins of the vestibular efferent fibers to the ampulla of the semicircular canals in cats were examined using retrograde transport of horseradish peroxidase (HRP).Of the three semicircular canals, two ampullae and the cochlea were completely destroyed and filled with bone wax and dental cement to avoid leakage of HRP into the other areas. Thereafter, in the little hole of the remaining ampulla of the intact canal, approximately 0.2mg of crystalline HRP was placed. HRP was applied into the ampulla of the anterior, lateral and posterior semicircular canals of 5, 4 and 5 cats, respectively.The ampulla of the anterior canal was innervated from the bilateral parvocellular nucleus (PCRN), contralateral gigantocellular reticular nucleus and ipsilateral lateral reticular nucleus (LRN); the ampulla of the lateral canal, from the ipsilateral PCRN and LRN as well as the ipsilateral lateral vestibular nucleus; the ampulla of the posterior canal, from the bilateral PCRN and ipsilateral medial and lateral vestibular nuclei.These results indicate that each ampulla of the three semicircular canals receives efferent fibers from different reticular nuclei and the vestibular nuclei.