CONNECTIONS BETWEEN THE SPINAL CORD AND THE NUCLEUS OF THE SOLITARY TRACT IN THE RABBIT / 解剖学报

ABSTRACT

HRP or WGA-HRP was injected into the rabbit cervical, thoracic, or lumbar spinal gray unilaterally and the retrograde labeled ceils and anterograde labeled terminal branches in the nucleus of the solitary tract were studied. The labeled cells were found in the caudal part of the nucleus. The amount of the labeled cells in the cervical and thoracic injection cases out numbered that of the lumbar cases. In all the cases labeled ceils were most concentrated near the obex level, mainly located ventromedial to the tract. Some could be found ventral, ven- trolateral, lateral and medial to and in the vicinity of the tract. In the medial part of the nucleus labeled cells were limited in its ventral part dorsal to the dorsal motor nucleus of the vagus nerve. No labeling could be ascertained in the subnucleus parvocellularis. In the thoracic injection cases a group of labeled cells were discovered dorsolateral to the tract where only a few labeled ceils could be found in the cervical and lumbar cases. Labeled terminal branches largely accompanied the labeledcells. Thus the chance of establishing direct synaptic contact between spino-solitary fibers and the spinal projection cells of the nucleus of the solitary tract is great. At the level of obex a narrow band of terminal labeling along the dorsolateral border of the nucleus was identified. Except occasionally no labeled cells were found in this zone, an area probably related to cardiac function.