Summary
Octopus synaptosomes have been examined after glutaraldehyde fixation and phosphotungstic acid (PTA) staining of non-osmicated tissue. The results concentrate on the appearance of the contact region between the presynaptic component of synaptosomes and their postsynaptic processes. Membranes have a triple-layered appearance, consisting of an electronopaque internal coat, an electrontranslucent band and an electronopaque external coat. Good examples of this are found in synaptosomal, dendritic and axonal membranes. At specialized synaptic contact regions the external coats of the pre- and postsynaptic membranes coalesce to form a prominent synaptic plate, which has a width of 18 nm and is subdivided into zones of varying electronopacity. It is suggested that this plate is formed from the specialized external coat of the postsynaptic membrane and the unspecialized external coat of the presynaptic membrane. Presynaptic spicules extend from the internal coat of the presynaptic membrane. They are closely associated with elements of the presynaptic network.
It is suggested that the synaptic plate is probably composed of mucopolysaccharides, while the relation of the plate to acetylcholinesterase is discussed. It is proposed that functional localization at the synapse is less precise in octopus than vertebrates.
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I would like to express my thanks to Professors J. Z. Young, F. R. S. and E. G. Gray for their helpful advice, and also Mr. S. Waterman for photographic assistance.
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Jones, D.G. A further contribution to the study of the contact region of Octopus synaptosomes. Z. Zellforsch. 103, 48–60 (1970). https://doi.org/10.1007/BF00335400
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DOI: https://doi.org/10.1007/BF00335400