Active state plateau and latency in mammalian striated muscle

¹ National Institute of Neurological Diseases and Blindness, National Institutes of Health, Bethesda, Maryland

The active state plateau in rat striated muscle was studied by superimposition of tension curves resulting from one and two stimuli. The plateau ends 4.0 ± 0.1 msec. after stimulation in rat striated muscle at 36°C. The time to the end of the plateau is 3.4 ± 0.1 times the latent period. During the plateau, response to a second stimulus appears after increased mechanical latency. The second stimulus can also result in tension development at rates nearly twice those reached after a single stimulus. This effect has a peak which about corresponds to the end of the active state plateau, but precedes the peak of the curve for maximum tension. Correct timing of the second stimulus can result in about 60% of tetanic tension. The use of thiopental, gallamine, tubocurarine and changes in muscle length did not affect these results.