Dependence of Intracellular End-Plate Action Potential on Adjacent Fiber Activity

¹ From the Department of Physiology and Biophysics, University of Washington School of Medicine, Seattle, Washington

Intracellular action potentials were recorded at the end plate and 1 mm away from it in small bundles of m. adductor longus of Rana pipiens during stimulation of the nerve. The end-plate spike reached a lower maximum and the repolarization was slower when compared with the spikes recorded 1 mm away. The difference was of the form expected from externally recorded impulses, and was much diminished when the number of fibers was reduced to two to three. It is suggested that asynchrony of the activity in adjacent fibers explains the lesser distortion of action potentials distant from the end plate.