KCl stimulation and ultrastructural responses of tannic acid-stained cholinergic synaptic terminals |
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| Authors: | Fox G Q Kriebel M E |
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| Institution: | 1. Max-Planck-Institut für biophysikalische Chemie, 37077, Göttingen, Germany;2. Department of Physiology, SUNY Upstate Medical Center, Syracuse, NY, U.S.A.;1. Department of Neurology, The Massachusetts General Hospital and NeuroDiscovery Center, Harvard Medical School, Boston, MA, USA;2. Grousbeck Gene Therapy Center, Schepens Eye Research Institute and Massachusetts Eye and Ear Infirmary, Boston, MA, USA;3. Ocular Genomics Institute, Department of Ophthalmology, Harvard Medical School, Boston, MA, USA;4. Harvard Program in Therapeutic Science, Harvard University, Cambridge, MA, USA;5. Harvard Stem Cell Institute, Harvard University, Cambridge, MA, USA;6. The Broad Institute of Harvard and MIT, Cambridge, MA, USA;1. Intelligent Polymer Research Institute, ARC Centre of Excellence for Electromaterials Science, AIIM Facility, University of Wollongong, Wollongong, NSW 2522, Australia;2. Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA |
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| Abstract: | The quantal-vesicular hypothesis equates miniature end-plate potentials (MEPPs) with fusions of synaptic vesicles. MEPP production thus predicts vesicle losses, increases in vesicle fusions and increases in terminal plasma membrane. MEPP production and these ultrastructural parameters have been evaluated in the cholinergic presynaptic terminals of skate electric organ following tannic acid saline incubation, known to promote capture and selective staining of dense-core granule fusions, and KCl stimulation, known to elevate MEPP production dramatically in these cholinergic terminals. After pretreatment in tannic acid-elasmobranch saline, KCl stimulation produced MEPPs at 40/s/microm(2)of terminal surface for several minutes with gradual reduction to spontaneous levels by 25-30 min. No loss of vesicles, no vesicle fusions, no expansions of plasma membrane and no tannic acid enhanced staining of vesicles or vacuoles accompanied the generation of 800 MEPPs/microm(3)of terminals having densities of 567 vesicles/microm(3). No ultrastructural footprints were found to support the notion that unnaturally high rates of vesicular exocytosis had occurred. |
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| Keywords: | exocytosis endocytosis MEPPs cholinergic synapses vesicle hypothesis |
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