THE INFLUENCE OF THE CALCIUM-ANTAGONIST VERAPAMIL ON THE EFFECTS OF BIOGENIC-AMINES IN INTACT AND ENDOTHELIUM-FREE BOVINE ABDOMINAL-AORTA

The calcium antagonist verapamil was found to depress the contractile effects of biogenic amines (noradrenaline, 5-hydroxytryptamine, histam ine) on the isolated bovine abdominal aorta. This effect was pronounce d both in intact and in endothelium-free preparations. The results ind icated that the contractile responses of the bovine abdominal aorta to biogenic amines were calcium-dependent. Nevertheless, the effect of v erapamil varied from one biogenic amine to the other. The conctractile responses of the abdominal aorta to noradrenaline and to histamine we re practically identical in intact and endothelium-free preparations. However, the effects of 5-hydroxytryptamine were more strongly inhibit ed by verapamil than the effects of the two other biogenic amines. Thu s, the effect of 5-hydroxytryptamine was almost completely blocked by verapamil in endothelium free kovine abdominal aorta. The effects of v erapamil were highly specific because they were easily reversed by inc reasing the extracellular concentration of calcium.