The effect of guanidine on the neuromuscular transmission in human intercostal and mouse
diaphragm muscle in vitro during repetitive nerve stimulation was studied. The drug greatly
increased the release of acetylcholine (ACh) quanta by nerve impulses at low frequencies of
nerve stimulation and at the beginning of tetani at high frequencies of stimulation. The effect
was shown to be produced by an increase in fractional release from an unchanged store of
ACh quanta available for immediate release. This seems to explain why guanidine has a …