[Vesicle cycle in mouse diaphragm motor nerve terminals].

In our research on mouse diaphragm muscles the dynamic of neurotransmitter secretion and synaptic vesicles recycling (exo-endocytosis cycle) at the long-term rhythmic stimulation (20Hz) are explored using an intracellular microelectrode registration and a fluorescent microscopy. It have been shown, thate change of end plant potentials (EPP) amplitude at the rhythmic training occurs in three phases: initial transient decrease, long amplitude stabilization (1-2 min)--the plateau and secondary slow decrease. After 3 minute stimulations the EPP amplitude recovery observed during several seconds. Loading the synaptic vesicle by fluorescent endocytic dye FM 1-43 had shown that the rhythmic stimulation results to gradual (during 5-6 mines) fluorescence decrease in NT, indicating the synaptic vesicle exocytosis. The quantum analysis of the electrophysiological data and their comparison to the fluorescent researches date has allowed to assume, that mouse motor nerve terminals are characterized by high rate of endocytosis and fast synaptic vesicle reuse (average recycling time about 50 sec) that can provide effective maintenance of synaptic transmission at long high-frequency activity. Sizes of ready releasable and recycling synaptic vesicle pools are quantitatively determined. It is assumed, that vesicle recycling occurs on a short fast way to inclusion in recycling pool. So, in the stimulation protocol that were used the synaptic vesicles from reserve pool remain unused. Thus in our conditions recycling pool vesicles cycle repeatedly without reserve pool release.