Excitation-Contraction Uncoupling: The Effect of Hyperosmolar Glycerol Solution and Dantrolene Sodium on Mammalian Muscle in Vitro

In the rat hemidiaphragm, in vitro dantrolene sodium irreversibly reduced twitch tension up to 20% of the original value in 20 minutes of exposure. The phenomenon was dose related. Dantrolene sodium did not affect (1) resting membrane potential (RMP); (2) miniature endplate potential frequency or amplitude; or (3) endplate potential amplitude decrement of repetitively stimulated partially curarized muscle. A combination of hyperosmolar solutions of glycerol and dantrolene sodium abolished contraction of mammalian muscle with no demonstrable effect on neuromuscular transmission or muscle fiber RMP. With this technique, prolonged recording from repetitively activated muscle fibers is possible.