Uni-quantal endplate currents (EPCs) were recorded extracellularly at the frog neuromuscular synapse and their latency dispersions expressed as P(90) were estimated in the presence of acetylcholine. Stimulation-evoked EPCs with long release latencies increased in number when acetylcholine was applied. P90, which is designated as the interval between the minimal synaptic delay and the time at which 90 per cent of all measured uni-quantal EPCs had occurred, was significantly and reversibly increased by 66 per cent from 0.51 ms to 0.85 ms in the presence of 5x10(-4) M acetylcholine. This indicates that the evoked release pattern is less synchronous and the increased asynchrony leads to a substantial drop (by 28 per cent) in the amplitude of reconstructed multi-quantal currents.

Institute of Physiology Academy of Sciences of the Czech Republic Vídenská 1083 142 20 Prague 4 Czech Republic

From Frog Muscle to Brain Neurons: Joys and Sorrows in Neuroscience