The control of muscle contracture by the action of dantrolene on the sarcolemma.

Although dantrolene reverses the muscle contracture seen during a malignant hyperpyrexia (MH) crisis, its site of action is not known. It has been inferred from previous work that the major abnormality in MH is in the sarcoplasmic reticulum, and that dantrolene must act on this organelle. In the present study the ability of dantrolene to control drug-induced muscle contraction was tested. The drugs were chosen because their sites of action were known for inducing contracture. Dantrolene had no effect on contractures induced by 2:4 dinitrophenol, exerted only a minor effect on caffeine contractions, but reduced significantly the contracture produced by K+. It is postulated that the major action of dantrolene is on the sarcolemma, which may be the site of the MH abnormality.