title: The effects of dantrolene on the contraction, relaxation, and energetics of the diaphragm muscle.
abstract: Dantrolene is used in patients with muscle spasticity and is the only known effective treatment for malignant hyperthermia. However, its effects on muscle relaxation and energetics are unknown and may have important consequences in diaphragmatic function. We studied the effects of dantrolene (10(-8) to 10(-4) M) on diaphragm muscle strips (n = 12) in the hamster in vitro (Krebs-Henseleit solution, 29 degrees C, 95% oxygen/5% carbon dioxide) in response to tetanic stimulation (50 Hz). We studied contraction and relaxation under isotonic and isometric conditions, as well as energetics. Data are mean +/- SD. Dantrolene induced a negative inotropic effect in the hamster diaphragm (active force at 10(-4) M: 34% +/- 7% of baseline; P < 0.05) but did not significantly modify the curvature of the force-velocity relationship. Dantrolene did not significantly modify isotonic relaxation. Dantrolene, up to 10(-5) M, did not significantly impair isometric relaxation. In conclusion, dantrolene induced a marked negative inotropic effect on diaphragm muscle without affecting myothermal efficiency and relaxation.
  
  
  CONCLUSIONS
  Dantrolene induced a significant and concentration-dependent negative inotropic effect on diaphragm muscle but did not modify isotonic relaxation, which suggests no alteration of the calcium reuptake by the sarcoplasmic reticulum; up to 10(-5) M dantrolene did not alter isometric relaxation, i.e., myofilament calcium sensitivity. Dantrolene did not modify the energetics of diaphragm muscle.
authors.affiliation: Department of Anesthesiology and Critical Care, Groupe Hospitalier Pitié-Salpêtrière, Paris VI University, France. olivier.langeron@psl.ap-hop-paris.fr
authors.forename: O
authors.initials: O
authors.lastname: Langeron
authors.forename: C
authors.initials: C
authors.lastname: Coirault
authors.forename: S
authors.initials: S
authors.lastname: Fratea
authors.forename: G
authors.initials: G
authors.lastname: Orliaguet
authors.forename: P
authors.initials: P
authors.lastname: Coriat
authors.forename: B
authors.initials: B
authors.lastname: Riou
mesh_terms: D000818:Animals; D006224:Cricetinae; D003620:Dantrolene / Q000494:pharmacology*; D003964:Diaphragm / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D008647:Mesocricetus; D009119:Muscle Contraction / Q000187:drug effects; D009125:Muscle Relaxants, Central / Q000494:pharmacology*; D009126:Muscle Relaxation / Q000187:drug effects
chemical_list: D009125:Muscle Relaxants, Central; D003620:Dantrolene