An analysis of the end‐plate potential recorded with an intra‐cellular electrode

According to present knowledge, the process of neuromuscular transmission can be described by the following scheme: nerve impulse -+ acetylcholine -end-plate potential -* muscle impulse -* contraction. The evidence for this chain has been summarized by Eccles (1948), Hunt & Kuffler (1950) and Rosenblueth (1950), whose reviews may be consulted for further references. While there is little doubt that acetylcholine is released by the nerve impulse and depolarizes the end-plate, the mechanism of these two actions is at present unknown and requires further investigation. The most immediate electrical sign of neuromuscular transmission is the end-plate potential, a local depolarization of the muscle fibre which is presumably due to the direct action of the neuromuscular transmitter. By measuring this electrical change under suitable conditions, some light can be thrown on the preceding steps of the transmission process. The object of this paper is to investigate the properties ofthe end-plate potential even more closely than has previously been attempted, making use of the method of intra-cellular recording which has been developed by Graham & Gerard (1946), Ling & Gerard (1949) and Nastuk & Hodgkin (1950). This method offers several advantages: resting and action potentials at individual junctions can be recorded in whole muscles, without microdisection or even removing the muscle from a Ringer bath, and the measurements do not suffer from uncertainties which are usually associated with the shunting effect of the interstitial fluid. The immediate concern of the present work is to determine the electric charge which passes through the end-plate membrane during the transmission of one impulse and to throw some light on the mechanism by which the transfer of ions across the end-plate is brought about.