[Changes in the ratio of quantum-vesicular parameters in the presence of disrupted synaptic transmitter secretion in the neuromuscular junctions of mammals].

To test the vesicular hypothesis of quantum release, some parameters of synaptic vesicles (SV) and miniature end plate potentials (MEPPs) were compared in phrenic neuromuscular junctions of rats poisoned with tetanus toxin (TT). The poisoning with TT that suppresses the transmitter release led to marked changes in the distribution of MEPPs amplitudes and SV diameters as compared to normal, namely to the transformation of unimodal histograms for both parameters to polymodal ones. The transformation was accompanied by a significant increase in variation coefficients of both distributions, thus indicating the disturbances of vesicle-quantum formation. The total number of SV in the poisoned terminal increased by 59% which might reflect both the lifetime situation characteristic for normal and/or real accumulation of the transmitter quanta as a result of the TT-hampered exocytosis through the presynaptic membrane, since during the reactivating action of ouabain, the transmitter release level from the poisoned terminal exceeded that for normal to about the same measure. The results obtained may be regarded as providing evidence in favour of the vesicular hypothesis.