Influence of papaverine, D600, and nifedipine on the effects of noradrenaline and calcium on the isolated aorta and mesenteric artery of the rabbit.

The effects of papaverine and of the organic calcium-antagonistic agents D 600 and nifedipine on the contraction induced by noradrenaline and calcium were studied on the isolated aorta and mesenteric artery. The affinities of both agonists, given as pD2-values, were significantly higher on the aorta than on the mesenteric artery. Under our experimental conditions D 600, nifedipine and papaverine were found to act as antagonists against calcium and noradrenaline in a non-competitive fashion. In either vessel, the calcium-antagonistic activity of D 600 and nifedipine was about 1000-fold greater than that of papaverine, whereas their antagonistic activity against noradrenaline was bout 1000-times weaker, i.e. D 600 as well as nifedipine were about equipotent with papaverine. The comparison between the calcium- and the noradrenaline-antagonistic activity offers the possiblity to evaluate the specifcity of calcium antagonistic agents.