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Duality of Secretory Inclusions in Neurones — Ultrastructure of the Corresponding Sites of Release in Invertebrate Nervous Systems
Author(s) -
Golding D.W.,
May Barbara A.
Publication year - 1982
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1982.tb00782.x
Subject(s) - exocytosis , biology , granule (geology) , ultrastructure , secretion , synaptic vesicle , vesicle , microbiology and biotechnology , membrane , microvesicles , secretory vesicle , neurochemical , biophysics , biochemistry , anatomy , neuroscience , microrna , gene , paleontology
Central nerve terminals have been examined for ultrastructural signs of release of neurochemical mediators in the annelids Nereis diversicolor, Harmothoe imbricata and Lumbricus terrestris. Two categories of presumptive secretory inclusions are readily distinguished. Exocytosis of ‘storage granules’ is widespread in the neuropile, and involves probable peptidergic terminals as well as more conventional terminals. Plasma membranes at such sites of release are apparently unmodified. In contrast, ‘synaptic vesicles’ are aggregated adjacent to membrane thickenings and specialized clefts, and signs of their fusion with the presynaptic membranes have been observed rarely. The presence of coated pits surmounting omega profiles involving storage granules may indicate that membrane is retrieved in the form of microvesicles from the site of exocytosis. Coated pits associated with synapses have only been observed in areas of membrane adjacent to presumed sites of vesicle exocytosis. The incidence of dual sites of release, often relating to individual terminals, may be indicative of the segregated storage and independent secretion of distinct active principles. Materials released by granule exocytosis may have the role of neuromodulators.