Comparative Effects of Benzquinamide and P-2565 on Cardiac Rate

Summary

The bradycardia produced by benzquinamide or by P-2565 is not related to central parasympathetic stimulation. Studies on the isolated cat heart indicate that P-2565 does not have a direct effect on the isolated myocardium. Benzquinamide and P-2565 have ganglionic blocking properties as indicated by the tetramethylammonium test. In addition, the ability of benzquinamide and P-2565 to antagonize the guanethi-dine depletion of NE in heart tissue should be considered as a factor influencing the peripheral action of these agents on heart rate.

The authors wish to acknowledge the capable technical assistance of Mr. Willie Treadwell and Mr. Daniel Walker. They also wish to thank Dr. S. Y. P'an of the Charles Pfizer Laboratories, Groton, Conn, for the generous supply of benzquinamide and P-2565.