Stimulation frequency alters the inotropic response of atrial muscle to bay K-8644

Abstract

The inotropic and chronotropic effects of BAY K-8644 were examined in isolated guinea pig atria. The compound increased both rate and contractile force. Sensitivity to the inotropic effect was enhanced by increasing stimulation frequency between 0.5 and 3.3 Hz. The maximum developed tension elicited by the agent was reduced at 3.3 Hz. At BAY K-8644 concentrations up of to 3 × 10 −5 M, no dysrhythmic effects or other toxic signs such as an increase in resting tension were observed. These results are consistent with the suggestion that BAY K-8644 acts as a partial ‘calcium agonist’.