title: Myocardial depression associated with effective refractory period prolongation after pentobarbital and procainamide but not after dantrolene.
abstract: Effective refractory period (ERP) and contractile force (CF) of isolated rabbit left atria were monitored before and during cumulative concentration-response curves to procainamide, pentobarbital and dantrolene. CF reductions and ERP increases were observed after addition of pentobarbital or procainamide. Dantrolene, however, atypically reduced CF without affecting ERP. The prolonged ERP correlated with simultaneous CF reductions during pentobarbital and procainamide activity. These results suggest that the sarcolemmal stabilizing effects of pentobarbital and procainamide could be related to CF reductions while the cardiac depression of dantrolene is unrelated to this action and, as in skeletal muscle, may result from intracellular activity.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003620:Dantrolene / Q000494:pharmacology*; D003864:Depression, Chemical; D004558:Electric Stimulation; D005260:Female; D006321:Heart / Q000187:drug effects*; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D010424:Pentobarbital / Q000494:pharmacology*; D011342:Procainamide / Q000494:pharmacology*; D011817:Rabbits
chemical_list: D003620:Dantrolene; D010424:Pentobarbital; D011342:Procainamide