Temperature effect on proximal to distal gradient of quantal release of acetylcholine at frog endplate.

The conduction velocity of the nerve terminal, mean quantal content, and release latencies of uniquantal endplate currents (EPCs) were recorded in proximal, central, and distal parts of the terminal by extracellular pipettes located 5, 50, and 100 microm from the end of myelinated nerve trunk. The spike conduction velocity, minimal latency, modal value of the latency histograms, and time interval during which 90% of EPCs released (P90) at distal, central, and proximal part of the frog nerve terminal have different temperature dependency between 10 degrees and 28 degrees C. As shown by the size and time-course of reconstructed multiquantal EPCs, the secretion synchronization, which is greatest in distal parts, compensates at least partly for the progressive slowing of spike conduction velocity in the proximodistal direction, in particular at lower temperatures.