ON THE NATURE OF THE LATENCY RELAXATION OF FROG SKELETAL MUSCLE

Abstract

1. Some properties of latency relaxation in frog skeletal muscle were investigated to explain the source of this phenomenon.2. The latency relaxation started 2 msec (at 19-20°C) or 3.5 msec (at 10-12°C) after the peak of the spike of membrane action potential.3. The latency relaxation was increased and hastened as the muscle was stretched within the certain limit, while it was decreased by further stretching. The latency relaxation was disappeared at the muscle length as 1.8 times long as the slack length, where twitch tension was no longer developed.4. The second stimulus given at the relaxation phase of the preceding twitch was effective in the initiation of the second latency relaxation, although its magnitude was smaller than that of the control.5. Changes in temperatures, some twitch potentiating ions and hypertonicity in Ringer solution caused the changes in the latency relaxation qualitatively similar to the changes in twitch tension.