location of the abducent nucleus and its dentate input "degeneration and fluorescence study in the rat"

ABSTRACT

Following the injection of the lateral rectus muscle of the eye with the fluorescing dye DAPI-Pr, labeled [fluorescing] nerve cells are found outside the internal genu of the facial nerve. In contrast to descriptions made by many authors, none is found contained within this genu. Degeneration fibers of the ipsilateral dentate nucleus are traced to the spot where the abducent nerve cells are located, and they are found to round up [terminating] at this spot. The findings explained the discrepancy in the literature concerning the dentatoabducent input; and made of the abducent nucleus to exemption when compared with those of the oculomotor and of the trochlear nuclei, for all these nuclei of the extraocular muscle receive such a direct cerebellar input. The dissociation, in place of the abducent nucleus from the other more conglomerated extraocular muscle nuclei is presumably a functional issue related to the independence of the lateral rectus muscle to a precedent firing of the trochlear nucleus. The initimate relationship of the abducent nucleus to the internal genu of the facial nerve is brought about, more likely by the consequence of the transformation of the spinal cord into brainsterm. Still, it lies outside it. In normal stained section no nerve cell is found within the confinement of the internal facial genu regardless of its kind