THE ACTION OF VERILOID UPON THE ISOLATED MAMMALIAN HEART

¹ Department of Pharmacology, Boston Univer8ity School of Medicine, Boston, Mass.

Positive and negative inotropic actions of Veriloid have been demonstrated in the isolated rabbit heart perfused with Locke's solution according to a modification of the coronary perfusion technique of Langendorff. The effect of rapid injections of single doses up to 10 microgm. and of moderate concentrations (up to 0.075 microgm./ml.) of continuously perfused Veriloid was one of positive inotropism.

The bradycardic effect induced by Veriloid in the intact animal has not been obtained in the isolated heart of the rabbit. Thus the bradycardic effect of Veriloid showed no direct cardiac component.

Inotropic effects have occurred independently of chronotropic effects.

Both tachycardia and irregularities in rhythm have been produced in the isolated rabbit heart with rapidly-injected high doses and with concentrations of continuously perfused Veriloid greater than 0.1 microgm./ml. These arrhythmias were qualitatively identical with those previously reported as following excessive intravenous doses (over 75 microgm./kgm.) in the intact dog. These effects represented a direct action of the drug upon the heart independent of the central nervous system.