Presynaptic effect of streptomycin on the insect neuromuscular junction

The effect of streptomycin on the neuromuscular junction of the cockroach leg muscle was studied by means of intracellular electrodes. The miniature excitatory postsynaptic potential (MEPSP) frequency decreased in the presence of 1 mM streptomycin. Double logarithmic plots of the quantal content against the external calcium concentration in the absence and presence of streptomycin suggested the competition for a common site of presynaptic membrane at insect neuromuscular junctions.