Studies of the halothane-cooling contractures of skeletal muscle

The characteristics of transient contractures elicited by rapid cooling of frog or mouse muscles perfused in vitro with solutions equilibrated with 0.5-2.0% halothane are reviewed. The data indicate that these halothane-cooling contractures are dose dependent and reproducible, and their amplitude is larger in muscles containing predominantly slow-twitch type fibers, such as the mouse soleus, than in muscles in which fast-twitch fibers predominate, such as the mouse extensor digitorum longus. The halothane-cooling contractures are potentiated in muscles exposed to succinylcholine. The effects of Ca2+-free solutions, of the local anesthetics procaine, procainamide, and lidocaine, and of the muscle relaxant dantrolene on the halothane-cooling contractures are consistent with the proposal that the halothane-cooling contractures result from synergistic effects of halothane and low temperature on Ca sequestration by the sarcoplasmic reticulum. Preliminary results from skinned rabbit muscle fibers support this proposal. The halothane concentrations required for the halothane-cooling contractures of isolated frog or mouse muscles are comparable with those observed in serum of patients during general anesthesia. Accordingly, fascicles dissected from muscle biopsies of patients under halothane anesthesia for programmed surgery develop large contractures when rapidly cooled. The amplitude of these halothane-cooling contractures declined with the time of perfusion of the muscle fascicles in vitro with halothane-free physiological solutions. It is suggested that the halothane-cooling contractures could be used as a simple experimental model for the investigation of the effects of halothane on Ca homeostasis and contractility in skeletal muscle and for study of drugs of potential use in the management of the contractures associated with the halothane-induced malignant hyperthermia syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)