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L‐type calcium channels are involved in fast endocytosis at the mouse neuromuscular junction
Author(s) -
Perissinotti Paula P.,
Tropper Bárbara Giugovaz,
Uchitel Osvaldo D.
Publication year - 2008
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2008.06113.x
Subject(s) - endocytosis , neuromuscular junction , microbiology and biotechnology , l type calcium channel , calcium , neuroscience , voltage dependent calcium channel , chemistry , biology , receptor , biochemistry , organic chemistry
We used fluorescence microscopy of FM dyes‐labeled synaptic vesicles and electrophysiological recordings to examine the functional characteristics of vesicle recycling and study how different types of voltage‐dependent Ca 2+ channels (VDCCs) regulate the coupling of exocytosis and endocytosis at mouse neuromuscular junction. Our results demonstrate the presence of at least two different pools of recycling vesicles: a high‐probability release pool (i.e. a fast destaining vesicle pool), which is preferentially loaded during the first 5 s (250 action potentials) at 50 Hz; and a low‐probability release pool (i.e. a slow destaining vesicle pool), which is loaded during prolonged stimulation and keeps on refilling after end of stimulation. Our results suggest that a fast recycling pool mediates neurotransmitter release when vesicle use is minimal (i.e. during brief high‐frequency stimulation), while vesicle mobilization from a reserve pool is the prevailing mechanism when the level of synaptic activity increases. We observed that specific N‐ and L ‐type VDCC blockers had no effect on evoked transmitter release upon low‐frequency stimulation (5 Hz). However, at high‐frequency stimulation (50 Hz), L ‐type Ca 2+ channel blocker increased FM2‐10 destaining and at the same time diminished quantal release. Furthermore, when L ‐type channels were blocked, FM2‐10 loading during stimulation was diminished, while the amount of endocytosis after stimulation was increased. Our experiments suggest that L ‐type VDCCs promote endocytosis of synaptic vesicles, directing the newly formed vesicles to a high‐probability release pool where they compete against unused vesicles.