title: Quantitative analysis of synaptic boutons on motoneurons of rhesus monkey spinal cord after chronic deafferentation due to cerebral lesions.
abstract: The motoneurons in the lateral nucleus of the anterior horn of the rhesus monkey cervical enlargement were reconstructed by light microscopy of semi-thin sections of 2 micro in thickness which were cut serially, alternately with ultra-thin sections for electron microscopy. Four single neurons were reconstructed with a computer graphic system, and simultaneously the synaptic boutons on the soma and each dendrite of single reconstructed neurons were analyzed quantitatively by electron microscopy. The synaptic boutons were classified into 4 types on the basis of the shape of the synaptic vesicles. The F-type boutons with flattened vesicles, S-type with spherical vesicles, G-type with cored vesicles and large L-type boutons with smaller and polymorphic vesicles, were almost identical to the boutons categorized by Bodian (1966b). The F-type boutons represented the major type in terms of the covering ratio and synaptic population. The S-type boutons tended to occur more frequently on dendrites. The motoneurons of the same region were also investigated in a similar manner after chronic deafferentation by the ablation of the upper extremity area of the left cerebral cortex. F-type of boutons were significantly increased, especially on the dendrites, compared with the synaptic distribution of the normal motoneurons.
mesh_terms: D000818:Animals; D000870:Anterior Horn Cells / Q000473:pathology*; D002540:Cerebral Cortex / Q000293:injuries*; D008253:Macaca mulatta; D008854:Microscopy, Electron; D009046:Motor Neurons / Q000473:pathology*; D013569:Synapses / Q000648:ultrastructure