Ouabain-Induced Negative Frequency-Force Relationship in the Isolated, Blood-Perfused Dog Atrium

抄録

Effects of ouabain, CaCl₂ and verapamil on the frequency-force relationship (FFR) were investigated in the isolated, blood-perfused dog atrial muscle preparation. When ouabain (3 and 10μg) or CaCl₂ (0.5, 1 and 2mg/min) was given into the sinus node artery, the contractile force of the atrial muscle, driven at a constant pacing rate of 2Hz, increased dose-dependently. Verapamil (1 and 3μg) decreased the atrial contractile force dose-dependently. When the pacing rate was changed from 2 to 3.5Hz, the atrial contractile force increased in parallel with the pacing rate (positive FFR). After treatment with ouabain and verapamil, the contractile force declined at higher frequencies (negative FFR). The verapamilinduced negative FFR was much steeper than the ouabain-induced relationship. An infusion of CaCl₂ modified the FFR such that higher doses of CaCl₂ elicited a negative FFR only at higher pacing rates. However, the CaCl₂-induced FFR did not differ from the negative FFR induced by verapamil or ouabain. It was demonstrated that the cardiotonic agents ouabain and CaCl₂, as well as verapamil induced negative FFR in the isolated dog heart.