title: Effects of halothane on transmembrane potentials, Ca2+ transients, and papillary muscle tension in the cat.
abstract: The effects of halothane on cat papillary muscle were studied in vitro at different pacing rates (60, 75, 100, and 150 beats/min). Simultaneous measurements of transmembrane potentials, intracellular Ca2+ transients, and isometric tension were made before and after introduction of 1 and 2 minimal alveolar concentration halothane. Anesthetic concentrations in the superfusion bath were measured using a gas chromatography procedure. The Ca2+-sensitive photoprotein, aequorin, was microinjected into papillary muscle cells. Aequorin light emission is a function of free intracellular [Ca2+] [( Ca2+]i). The most prominent effects of halothane were a dose-dependent decrease in the contractile force and a decrease in [Ca2+]i, at all pacing rates. The negative inotropic effect of halothane was associated with only small changes in the papillary muscle action potential duration. Increasing the extracellular [Ca2+] produced an increase in [Ca2+]i and counteracted the negative inotropic effects of halothane. Addition of the Ca2+ channel blocker, verapamil, and halothane, produced an additive decrease in [Ca2+]i compared with the control.
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000331:Aequorin; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002415:Cats; D006221:Halothane / Q000494:pharmacology*; D006339:Heart Rate; D008564:Membrane Potentials / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects*; D009994:Osmolar Concentration; D010210:Papillary Muscles / Q000502:physiology*; D012044:Regression Analysis; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000331:Aequorin; D014700:Verapamil; D002118:Calcium; D006221:Halothane