Internuclear fiber connections of vestibular nuclear complex. A horseradish peroxidase study

Internuclear fiber connections among the superior (SVN), lateral (LVN), medial (MVN) and descending (DVN) vestibular nuclei were examined in cats using retrograde transport of horseradish peroxidase (HRP). HRP was microiontophoretically applied in the respective vestibular nucleus at doses of 300-500 nA for 5-10 min, and with the treatment the HRP injection site was limited to 0.2-0.5 mm in diameter within the nucleus. Major commissural connections were found between the bilateral SVN and between the bilateral DVN. Minor commissural connections were observed from MVN to SVN, LVN and MVN, from DVN to LVN, and from LVN to the contralateral LVN. In the ipsilateral vestibular nuclei, fiber connections were found from LVN to SVN, from MVN to SVN, LVN and DVN, and from DVN to SVN and LVN.