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Recycling of Synaptic Vesicles at the Frog Neuromuscular Junction in the Presence of Strontium
Author(s) -
Guatimosim Cristina,
RomanoSilva Marco A.,
Gomez Marcus V.,
Prado Marco A. M.
Publication year - 1998
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1998.70062477.x
Subject(s) - exocytosis , endocytosis , calcium , synaptic vesicle , internalization , strontium , neuromuscular junction , biophysics , chemistry , extracellular , stimulation , vesicle , microbiology and biotechnology , biology , biochemistry , neuroscience , cell , membrane , organic chemistry
In these experiments, we followed the exocytosis and endocytosis of synaptic vesicles with the vital dye FM1‐43 and asked whether calcium is important for membrane retrieval at the frog neuromuscular junction. We replaced calcium with equimolar amounts of strontium and monitored the staining of recycling vesicles by inducing exocytosis with electrical stimulation. Trains of 2,400 (2 or 20 Hz) or 4,200 (20 Hz) pulses failed to induce FM1‐43 internalization in the presence of strontium, but they did in the presence of calcium. This effect of strontium was not due to a decrease in exocytosis, because FM1‐43 release was similar in the presence of calcium or strontium. The impairment in endocytosis, observed as inhibition of FM1‐43 internalization, could be overcome by longer periods of stimulation (6,000 pulses at 2 or 20 Hz) in the presence of strontium (1.8 m M ) or by increasing the extracellular concentration of strontium to 10 m M (2,400 action potentials at 20 Hz). It is suggested that endocytosis is dependent on calcium influx and that strontium is much less effective in replacing calcium for endocytosis than it is for exocytosis.