SPINAL PROJECTIONS FROM THE RHOMBENCEPHALON IN THE TOAD

  • 1 January 1981
    • journal article
    • research article
    • Vol. 119  (2) , 139-150
Abstract
Rhombencephalic cell groups projecting to the spinal cord were demonstrated following single pressure injections and/or iontophoretic ejections of HRP [horseradish peroxidase] solution in either cervical or lumbar enlargements of the toad B. bufo spinal cord. A group uptake and transport of HRP were obtained with both application techniques, when sufficiently long survival times (8-II days) were used. Following injections in the cervical cord labeled cells are located mostly in the ventral nucleus of the VIIIth nerve and in the medial zone of the rhombencephalic reticular formation, i.e., the nucleus reticularis inferior, medius and superior. Following injections in the lumbar enlargement the majority of labeled cells are situated in the caudalmost portion of the ventral nucleus of the VIIIth nerve and in the nucleus reticularis inferior. In the toad the main supraspinal descending pathways from the rhombencephalon originate in the ventral nucleus of the VIIIth nerve and the medial zone of the reticular formation. Both these pathways are apparently somatotopically organized.