BRAIN-STEM PROJECTIONS OF DIFFERENT BRANCHES OF THE VESTIBULAR NERVE - AN EXPERIMENTAL-STUDY BY TRANSGANGLIONIC TRANSPORT OF HORSERADISH-PEROXIDASE IN THE CAT .1. THE HORIZONTAL AMPULLAR AND UTRICULAR NERVES

  • 1 January 1983
    • journal article
    • research article
    • Vol. 121  (4) , 237-248
Abstract
Adult cats (27) were used to study the central projection of the horizontal ampullar nerve and the utricular nerve using transganglionic transport of HRP [horseradish peroxidase]. The nerve investigated was exposed transtympanally cut and a capsule containing 50% HRP applied to the proximal stump for 1 h; 2-8 days later the animals were perfused. Frozen serial sections were cut from the brainstem and processed for the demonstration of HRP using tetramethyl benzidine as chromogen. Maximal labeling was observed 5-7 days postoperatively. After application of HRP to the horizontal ampullar nerve extensive labeling was found in all 4 main nuclei except the lateral vestibular nucleus. Labeling was observed in the interstitial nucleus of nerve VIII, the rostral part of the external cuneate nucleus and in the reticular formation laterodorsal to the abducens nucleus. Small fibers were also seen in the brachium conjunctivum oriented towards the cerebellum, from the superior vestibular nucleus. After exposing the utricular nerve to HRP, labeling was observed in the ventral part of the lateral vestibular nucleus, the central part of the medial vestibular nucleus and in the rostral part of the descending vestibular nucleus. Findings are discussed in relation to known physiological differences between the 2 kinds of nerves investigated.