Comparative studies of cerebral vasodilators on relaxation activities in isolated basilar, mesenteric and pulmonary arteries of rabbits.

Effects of cerebral vasodilators such as bencyclane, cinnarizine, and papaverine were comparatively studied using helically cut basilar and superior mesenteric arteries and radial muscle preparations of pulmonary arteries with the sympathetic nerve isolated from rabbits. The order of relaxation activities on high K+-induced contractures was cinnarizine>bencyclane>papaverine in basilar strips and cinnarizine>papaverine>bencyclane in mesenteric strips. Relaxation responses of basilar strips to cinnarizine and bencyclane were faster and more marked than those seen in mesenteric strips. Responses to papaverine were equipotent in both preparations. The action of cinnarizine alone was irreversible. In mesenteric strips, the order of the sensitivity of contractile responses to cumulatively applied biogenic amines was serotonin>noradrenaline>histamine. Cinnarizine produced an antihistaminergic action, while bencyclane produced an antiserotonergic action. In pulmonary arteries, 6 x 10(-6) g/ml papaverine inhibited contractile responses to 2, 5, and 25 Hz nerve stimulation in a frequency-independent manner together with inhibition of responses to noradrenaline. Bencyclane at 6 x 10(-6) and 10(-5) g/ml selectively inhibited in a dose-dependent manner contractile responses only to 25 Hz without inhibition of responses to noradrenaline. These results were discussed in comparison with findings of the cerebral vasodilators obtained using other experimental techniques. Spiral strips of basilar arteries from rabbits in combination with peripheral arteries may be used as a simple quantitative, and reproducible screening method in a preclinical stage for drug evaluation of cerebral vasodilators.