抄録
Surface potential of the excised toad's muscle, mostly sartorius, was recorded by a method similar to that used by Burns and Paton (1). Distribution of the surface potential along the length axis of muscle was demonstrated as a curve on a cathode-ray tube.
1. Surface potential of an intact muscle is almost equal, demonstrating a difference of less than 1 mV. When 10-4-10-5 ACh chloride is applied, one or two negative peaks appear in the pattern of surface potential. This peak is due to ACh depolarization of the end-plate membrane. If a fine electrode is used, the shape of this peak becomes sharp.
2. Actions of ACh in sodium-free media were studied. It was proven that ACh depolarization of the end-plate occurs in a sodium-free medium where sucrose Ringer and NH4+ Ringer are mixed at an even rate (table 1). After being soaked in this medium, the muscle tested shows ACh depolarization just as in the pre-treatment stage. A vigorous ACh contracture is also observed. The results seem to support strongly the short circuit theory of end-plate depolarization (2, 3, 5, 6, 7, 8).
3. Patterns of ACh depolarization were recorded in several different muscles other than the sartorius. Two types of patterns are found in ACh depolarization. In the first type, which is represented by the sartorius muscle, the peak is sharp and distinct. In the second type, which is represented by the rectus abdominis, the peak is flat. It is considered that muscles which belong to the latter group are composed mostly of tonus fibers.
