Membrane potential dependence of potential oscillation induced by cevadine in striated muscle.

The dependence of the membrane potential oscillation induced by cevadine on the actual transmembrane potential was studied in the frog sartorius muscle. 1. If the membrane potential oscillation is recorded for hours, its amplitude is seen to decrease slowly and smoothly and the membrane potential measured during the resting period among the waves of oscillation also decreases simultaneously. This means that the depolarization increases. 2. The increase of depolarization results not only in a decrease in the amplitude of the oscillation but the oscillation ceases between -40 and -55 mV as well. 3. The phenomenon reappears if the membrane is partially repolarized on a cevadine treated muscle fibre on which the membrane potential oscillation has already ceased as a consequence of the relatively marked depolarization. 4. Changing the membrane potential either to a value more positive than -40 mV, or to one more negative than -90 mV the developed oscillation activity may reversibly be suspended. 5. According to the above results, the amplitude of the membrane potential oscillation depends on the actual membrane potential. If other factors which may influence the oscillation parameters are unchanged, the relationship between the oscillation amplitude and the membrane potential can be characterized by a linear equation. In these cases there is a close correlation between the measured values and the calculated ones.