title: Inotropic effect of amrinone in rabbit papillary muscle: reversal of the myocardial depressant effect of halothane.
abstract: In rabbit papillary muscles, the pronounced inotropic effect of amrinone (0.4-0.8 mg/mL) observed at low stimulation frequencies (0.1-0.5 Hz) diminished as the frequency was increased to 1.0-2.0 Hz. Reversal of the negative inotropic effect of halothane (1%) by amrinone (0.8 mg/mL) was similarly dependent on stimulation frequency. The contractile response to paired-pulse stimulation in the presence of amrinone (0.8 mg/mL) was summation rather than postextrasystolic potentiation. Amrinone (0.8 mg/mL) was not effective in reversing the negative inotropic effect of halothane (1%) on potentiated state contraction generated by paired-pulse stimulation. These results suggest that amrinone increases the influx of extracellular Ca2+ across the sarcolemma but not the availability of cellular Ca2+ which accumulates, most likely in sarcoplasmic reticulum, under the condition of potentiation.
mesh_terms: D000631:Aminopyridines / Q000494:pharmacology*; D000676:Amrinone; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000037:antagonists & inhibitors*; D004558:Electric Stimulation; D006221:Halothane / Q000037:antagonists & inhibitors*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D010210:Papillary Muscles / Q000187:drug effects*; D011817:Rabbits
chemical_list: D000631:Aminopyridines; D000889:Anti-Arrhythmia Agents; D000676:Amrinone; D006221:Halothane