Comparative study of neuronal and glial gap-junctions in crayfish nerve cords.
Electrical synapses (neuronal gap-junctions) and glial gap-junctions were compared by using thin sectioning, freeze fracturing, and negative staining techniques. Neuronal and glial gap-junctions differed in the length of the extracellular domains of the channels, in the presence of a cytoskeleton associated to neuronal gap-junctions, and in their unit cell dimensions. The difference in length of the channels and the fact that both glial and neuronal gap-junctions had the same particle diameter suggest that the proteins forming glial and neuronal gap-junctions might have different molecular weights. The cytoskeleton associated to neuronal gap-junctions consisted of a beaded layer of densities located parallel to the membrane in the synaptic regions. Synaptic vesicles associated to neuronal gap-junctions were attached to this cytoskeleton, which was in turn anchored to the synaptic membrane through densities about 20 nm apart, a spacing similar to the neuronal unit cell dimension. These results suggest that the cytoskeleton might be responsible for the association of vesicles to neuronal gap-junctions and for maintaining the crystalline appearance of neuronal gap-junctions in situ.
Bosch
E
E
Department of Physiology, University of California, Los Angeles 90024.
D000005:Abdomen / Q000294:innervation; D000818:Animals; D003400:Astacoidea / Q000033:anatomy & histology*; D003599:Cytoskeleton / Q000648:ultrastructure; D004594:Electrophysiology; D005614:Freeze Fracturing; D006652:Histological Techniques; D007365:Intercellular Junctions / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009457:Neuroglia / Q000648:ultrastructure*; D009474:Neurons / Q000648:ultrastructure*; D013194:Staining and Labeling; D013569:Synapses / Q000648:ultrastructure