title: Two types of spontaneous contractions in rat myocardium and their possible relation to different Ca release processes.
abstract: The potency of putative blockers (lidocaine, dantrolene Na, DAN, SKF 525A) for various forms of Ca2+ release from sarcoplasmic reticulum (SR) against two types of spontaneous contractions induced by 0.5 mM caffeine (caffeine response) or myocardium Ca2+ overload (after-contractions) was tested in rat papillary muscle. There were differences in the sensitivity of spontaneous contractions to the agents employed. The caffeine response was depressed by DAN but not affected by lidocaine. Conversely, conventional diastolic after-contractions were eliminated by lidocaine and SKF 525A but DAN failed to affect them. The two types of spontaneous contractions were suggested to be triggered by different CA2+ release processes supposedly originating from different SR compartments.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003042:Cocaine / Q000494:pharmacology; D003620:Dantrolene / Q000494:pharmacology; D066298:In Vitro Techniques; D008012:Lidocaine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000378:metabolism*; D011335:Proadifen / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D008012:Lidocaine; D011335:Proadifen; D003620:Dantrolene; D003042:Cocaine; D002118:Calcium