脊髄の樹状突起束:とくにOnuf核と横隔神経核について

Abstract

Large dendrite bundles (LDBs) of the perineal and phrenic motoneurons (MNs) were observed light and electron microscopically in the cat, dog, and Japanese monkey after labeling the MNs by the horseradish peroxidase (HRP) method. No special differences were noted in the structural features of the LDBs among the animals used in the present study. The LDBs were composed of longitudinally-oriented 1, 000-2, 000 dendrites, and interspersed with somata of the MNs, myelinated nerve fibers, glial cells, and blood capillaries. The diameter of the LDBs ranged from 200 μm to 400 μm. On occasions dendritic membranes were in casual apposition for a considerable distance. Desmosome-like junctions were also found infrequently between adjacent dendrites. Neither gap junctions nor dendrodendritic synapses, however, were found. Dendrite bundles of the phrenic MNs were also examined in the cat after labeling the phrenic MNs with HRP injected into the diaphragm. Within the confines of the phrenic nucleus, 20-30 dendrite bundles were seen; each of these dendrite bundles was composed of 10-60 dendrites. Other ultrastructural features of the dendrite bundles of the phrenic MNs were essentially the same as those of the perineal MNs. Possible functional significance of the dendrite bundles of MNs was discussed.