抄録
1. In Cl-free sulphate-, ferrocyanide-and glutamate-Ringer's solutions, the frog skeletal muscle fiber showed two different distributions of the resting potentials, one of which had the peak at about -80mV and the other, about-30mV. The difference of the resting Potentials in two groups was clear in K-free solution.
2. The fiber with the low resting potential had a much higher membrane resistance than that of the fiber with the high resting potential. The low resting potential seemed to correspond to the plateau of the prolonged action potential at which both Na and K conductances were inactivated. In such condition, the fiber showed the slow break response after cessation of the strong inward current pulse. The response may be caused by the increase of the K-conductance due to the hyperpolarization. Form of the response was varied depending on the membrane potential level.
3. In K-rich Cl-free solution, the slow break response was also observed after termination of the inward current pulse. This response may be explained by the decrease of the K-conductance due to the hyperpolarization.
