Malignant hyperthermia and related neuromuscular diseases: caffeine contracture of the skinned muscle fibers.

Using the skinned fiber preparation, the response to caffeine was studied on the skeletal muscle of malignant hyperthermia or other neuromuscular diseases. The sensitivity to caffeine was increased in the muscle of malignant hyperthermia. The sensitivity also was increased in Duchenne muscular dystrophy or asymptomatic patients with raised serum creatine kinase activity. Judging from the interaction between caffeine and the contractile system, the abnormal response originated from the sarcoplasmic reticulum in malignant hyperthermia. In Duchenne muscular dystrophy, the contractile system also might be involved in the increased sensitivity. Since the disease spectrum presenting abnormal responses is broad, it is suggested that muscle fibers become sensitive to caffeine when they are degenerating or regenerating.