[Morphometry of the vesicular apparatus of the neuromuscular junction with different modes of transmitter release]

Neuromuscular junctions in the diaphragm muscle of rats were studied, using a usual chemical fixation technique and quick prefreezing of the muscle. The number of synaptic vesicles in the vicinity of presynaptic membrane decreased significantly during synaptic function activation. Quantitative investigation of axon terminal vesicle apparatus revealed heterogeneity in the size of synaptic vesicle pool. The pattern of synaptic vesicle size distribution in different functional states of the synapse suggests that size heterogeneity reflects their functional peculiarities.