N. F. Skorobovichuk, L. Filippova
Dec 1, 1970
Summary1.Differences between responses of phasic and intermediate muscle fibers in frogs to prolonged depolarization by a current of threshold strength were investigated with intracellular microelectrodes.2.Intermediate fibers have a greater tendency toward repetitive spike responses to prolonged depolarization than phasic fibers. This is expressed by the fact that the percentage of fibers responding to threshold depolarization by a series of APs (instead of single APs) is much higher in the group of intermediate, fibers than in the phasic group. In addition, the duration of the repetitive response to depolarization was always greater in intermediate fibers.3.Agents such as calcium ions and procaine, which depress rhythmic activity in both phasic and intermediate fibers, differ in their quantitative action on these two groups of fibers: concentrations of agents which completely suppress the rhythmic response in phasic fibers merely shorten the duration of the rhythmic discharge in intermediate fibers.