Quantitative analysis of synaptic boutons on motoneurons of rhesus monkey spinal cord after chronic deafferentation due to cerebral lesions
Inoue, Y.; Inoue, K.; Terashima, T.; Nishimura, Y.; Shimai, K.
Journal für Hirnforschung 25(5): 527-536
1984
ISSN/ISBN: 0021-8359 PMID: 6501868 Document Number: 238329
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.