1. v. administration of 5,6-dimethoxy-2-(3-[(alpha-(3,4-dimethoxy) phenylethyl) methylamino] propyl)-
phthalimidine (AQ-A 39) to anaesthetized animals induced dose dependents
bradycardia. A comparison of the cardiovascular actions of
AQ-A 39 to those of the chemically related Ca2+-antagonist
verapamil in anaesthetized cats revealed that
AQ-A 39 reduced heart rate more that arterial blood pressure of left ventricular dpldtmax, whereas
verapamil was more active in decreasing blood pressure and myocardial contractility that in reducing heart rate. The corresponding ED20% (mg/kg i.v.) for
AQ-A 39 were 0.5 (heart rate), 2.9 (mean arterial blood pressure) and 1.8 (dp/dt max). The respective ED20% for
verapamil were 1.2, 0.06 and 0.08 mg/kg i.v. Decrease in dp/dt max following injection of
AQ-A 39 but not of
verapamil could be abolished or diminished by cardiac pacing. So the inotropic effect following i.v. administration of
AQ-A 39 were mainly due to interval-strength relationship. Cardiac output was much less decreased than heart rate since there was a significant increase in stroke volume in both anaesthetized cats and dogs. Peripheral resistance was not significantly influenced by systemic administration of
AQ-A 39. In anaesthetized dogs
AQ-A 39 (0.5 and 2.0 mg/kg i.v.) reduced myocardial oxygen consumption without impairing cardiac work output (i.e., mean aortic pressure X cardiac output).
AQ-A 39 induces cardiovascular actions which might be of benefit in the treatment of ischaemic
heart disease.