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Topography and Affinity of Calcium Sensors of Exo- and Endocytosis in Motor Nerve Terminals
Measurements with extracellular microelectrode technique showed that depolarization of motor nerve terminals in frog cutaneous pectoris muscle with high-potassium solution (40 mM K⁺) increased frequency of miniature end-plate currents. Both fast intracellular calcium chelator BAPTA-AM and slow chela...
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Published in: | Bulletin of experimental biology and medicine 2008-12, Vol.146 (6), p.667-670 |
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Main Authors: | , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites |
Online Access: | Get full text |
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Summary: | Measurements with extracellular microelectrode technique showed that depolarization of motor nerve terminals in frog cutaneous pectoris muscle with high-potassium solution (40 mM K⁺) increased frequency of miniature end-plate currents. Both fast intracellular calcium chelator BAPTA-AM and slow chelator EGTA-AM equally moderated the increase in the frequency of miniature end-plate currents. Intravital fluorescent microscopy with FM 1-43 dye showed that under conditions of stimulation of neurotransmitter exocytosis and secretion with high-potassium solution, internalization of the dye into newly-formed endocytotic synaptic vesicles proceeded both in the control and in the presence of EGTA-AM. In contrast, internalization of the dye was not observed in the presence of BAPTA-AM. It was concluded that asynchronous exocytosis of synaptic vesicles goes on in the active zones enriched with Ca-channels due to activation of highaffinity Ca-site in Ca-macrodomain. Endocytosis of vesicles is probably initiated by Camicrodomain during activation of low-affinity Ca-site in the immediate proximity to the Ca channel. |
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ISSN: | 0007-4888 1573-8221 |
DOI: | 10.1007/s10517-009-0369-6 |