IFIBYNE   05513
INSTITUTO DE FISIOLOGIA, BIOLOGIA MOLECULAR Y NEUROCIENCIAS
Unidad Ejecutora - UE
artículos
Título:
L-type calcium channels are involved in fast endocytosis at the mouse neuromuscular junction
Autor/es:
PAULA P. PERISSINOTTI, BA´RBARA GIUGOVAZ TROPPER AND OSVALDO D. UCHITEL
Revista:
EUROPEAN JOURNAL OF NEUROSCIENCE
Referencias:
Año: 2008 vol. 27 p. 1333 - 1344
ISSN:
0953-816X
Resumen:
We used fluorescence microscopy of FM dyes-labeled synaptic vesicles and electrophysiological recordings to examine thefunctional characteristics of vesicle recycling and study how different types of voltage-dependent Ca2+ channels (VDCCs) regulatethe coupling of exocytosis and endocytosis at mouse neuromuscular junction.Our results demonstrate the presence of at least twodifferent pools of recycling vesicles: a high-probability release pool (i.e. a fast destaining vesicle pool), which is preferentially loadedduring the first 5 s (250 action potentials) at 50 Hz; and a low-probability release pool (i.e. a slow destaining vesicle pool), which isloaded during prolonged stimulation and keeps on refilling after end of stimulation.Our results suggest that a fast recycling poolmediates neurotransmitter release when vesicle use is minimal (i.e. during brief high-frequency stimulation), while vesiclemobilization from a reserve pool is the prevailing mechanism when the level of synaptic activity increases.We observed that specificN- and L-type VDCC blockers had no effect on evoked transmitter release upon low-frequency stimulation (5 Hz). However, at highfrequencystimulation (50 Hz), L-type Ca2+ channel blocker increased FM2-10 destaining and at the same time diminished quantalrelease. Furthermore, when L-type channels were blocked, FM2-10 loading during stimulation was diminished, while the amount ofendocytosis 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.