Localizing the site of generation of uni-quantal endplate potentials using two intracellular microelectrodes

By recording with a microelectrode at either end of the endplate, the site of generation of uni-quantal endplate potentials (EPP) can be estimated. One method assumes that the logarithm of the amplitude of the signal declines linearly with distance along the cable [4, 8]. The uncertainties in this method are discussed. We show that even on a muscle cable the logarithm of the time integral of the EPP declines linearly with distance, falling to 1/e at a distance equal to the length constant, lambda. We conclude that the integral approach provides a theoretically sound method for localizing the sites of uniquantal EPP generation with two microelectrodes.