BACKGROUND: Porcine malignant hyperthermia (MH) can be triggered by administration of certain serotonin2 receptor agonists. Pretreatment with dantrolene completely abolished serotonin-induced MH. The purpose of this study was to investigate the effects of the serotonin2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in skeletal muscle specimens from MH-susceptible (MHS) and MH-nonsusceptible (MHN) patients following pretreatment with dantrolene. METHOD: We used muscle specimens surplus to diagnostic requirements from 12 MHS and 13 MHN patients in this study. In the first experiment, DOI 0.02 mM was added to the organ bath. In the second experiment, muscle specimens were preincubated with dantrolene 0.5 microM or 1.0 microM, respectively, for 10 min before DOI 0.02 mM was administered. RESULTS: Administration of DOI 0.02 mM induced contractures in muscle specimens from MHS and MHN patients. Contracture development started significantly earlier in MHS than in MHN specimens. In MHS muscle the maximum contracture was significantly greater than in MHN. Pretreatment with dantrolene significantly delayed the start of contracture development in MHS muscles, whereas in MHN muscles no contractures were observed after dantrolene. The contracture maximum was significantly reduced in MHS. CONCLUSION: The acceleration of DOI-induced contracture development in skeletal muscle specimens from MHS patients indicates that an altered serotonin system might be involved in human MH. Dantrolene effectively delayed serotonin-induced contractures. Further investigations are needed to determine whether serotonin2 receptors of skeletal muscle from MHS subjects are altered in function or structure, or whether this response is a secondary phenomenon.
BACKGROUND: Porcine malignant hyperthermia (MH) can be triggered by administration of certain serotonin2 receptor agonists. Pretreatment with dantrolene completely abolished serotonin-induced MH. The purpose of this study was to investigate the effects of the serotonin2 receptor agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) in skeletal muscle specimens from MH-susceptible (MHS) and MH-nonsusceptible (MHN) patients following pretreatment with dantrolene. METHOD: We used muscle specimens surplus to diagnostic requirements from 12 MHS and 13 MHN patients in this study. In the first experiment, DOI 0.02 mM was added to the organ bath. In the second experiment, muscle specimens were preincubated with dantrolene 0.5 microM or 1.0 microM, respectively, for 10 min before DOI 0.02 mM was administered. RESULTS: Administration of DOI 0.02 mM induced contractures in muscle specimens from MHS and MHN patients. Contracture development started significantly earlier in MHS than in MHN specimens. In MHS muscle the maximum contracture was significantly greater than in MHN. Pretreatment with dantrolene significantly delayed the start of contracture development in MHS muscles, whereas in MHN muscles no contractures were observed after dantrolene. The contracture maximum was significantly reduced in MHS. CONCLUSION: The acceleration of DOI-induced contracture development in skeletal muscle specimens from MHSpatients indicates that an altered serotonin system might be involved in human MH. Dantrolene effectively delayed serotonin-induced contractures. Further investigations are needed to determine whether serotonin2 receptors of skeletal muscle from MHS subjects are altered in function or structure, or whether this response is a secondary phenomenon.