Synapses on motoneuron dendrites in the brachial section of the frog spinal cord: a computer-aided electron microscopic study of cobalt-filled cells.

Détails

ID Serval
serval:BIB_7FCBB6CAA042
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
Synapses on motoneuron dendrites in the brachial section of the frog spinal cord: a computer-aided electron microscopic study of cobalt-filled cells.
Périodique
Journal of neurocytology
Auteur⸱e⸱s
Antal M., Kraftsik R., Székely G., van der Loos H.
ISSN
0300-4864
Statut éditorial
Publié
Date de publication
1992
Peer-reviewed
Oui
Volume
21
Numéro
1
Pages
34-49
Langue
anglais
Résumé
Cobalt-labelled motoneuron dendrites of the frog spinal cord at the level of the second spinal nerve were photographed in the electron microscope from long series of ultrathin sections. Three-dimensional computer reconstructions of 120 dendrite segments were analysed. The samples were taken from two locations: proximal to cell body and distal, as defined in a transverse plane of the spinal cord. The dendrites showed highly irregular outlines with many 1-2 microns-long 'thorns' (on average 8.5 thorns per 100 microns 2 of dendritic area). Taken together, the reconstructed dendrite segments from the proximal sites had a total length of about 250 microns; those from the distal locations, 180 microns. On all segments together there were 699 synapses. Nine percent of the synapses were on thorns, and many more close to their base on the dendritic shaft. The synapses were classified in four groups. One third of the synapses were asymmetric with spherical vesicles; one half were symmetric with spherical vesicles; and one tenth were symmetric with flattened vesicles. A fourth, small class of asymmetric synapses had dense-core vesicles. The area of the active zones was large for the asymmetric synapses (median value 0.20 microns 2), and small for the symmetric ones (median value 0.10 microns 2), and the difference was significant. On average, the areas of the active zones of the synapses on thin dendrites were larger than those of synapses on large calibre dendrites. About every 4 microns 2 of dendritic area received one contact. There was a significant difference between the areas of the active zones of the synapses at the two locations. Moreover, the number per unit dendritic length was correlated with dendrite calibre. On average, the active zones covered more than 4% of the dendritic area; this value for thin dendrites was about twice as large as that of large calibre dendrites. We suggest that the larger active zones and the larger synaptic coverage of the thin dendrites compensate for the longer electrotonic distance of these synapses from the soma.
Mots-clé
Animals, Cobalt, Dendrites, Image Processing, Computer-Assisted, Lysine, Microscopy, Electron, Motor Neurons, Rana esculenta, Spinal Cord, Synapses
Pubmed
Web of science
Création de la notice
30/03/2009 10:46
Dernière modification de la notice
20/08/2019 14:40
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